- Email: [email protected]
Habitat odor can alleviate innate stress responses in mice
BRES : 44566
pp: 127ðcol:fig: : NILÞ
Model7 brain research ] (]]]]) ]]]–]]]
121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 Q1 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180
Available online at www.sciencedirect.com
www.elsevier.com/locate/brainres
Research report
Habitat odor can alleviate innate stress responses in mice Mutsumi Matsukawaa,n, Masato Imadaa, Shin Aizawaa, Takaaki Satob a
Division of Anatomical Science, Department of Functional Morphology, Nihon University School of Medicine, 30-1 Oyaguchi-Kamicho, Itabashi, Tokyo 173-8610, Japan b Biomedical Research Institute, National Institute of Advanced Industrial Science and Technology, 1-8-31 Midorigaoka, Ikeda, Osaka 563-8577, Japan
art i cle i nfo
ab st rac t
Article history:
Predatory odors, which can induce innate fear and stress responses in prey species, are frequently
Accepted 12 November 2015
used in the development of animal models for several psychiatric diseases including posttraumatic stress disorder (PTSD) following a life-threatening event. We have previously shown that odors can be divided into at least three types; odors that act as (1) innate stressors, (2) as
Keywords:
innate relaxants, or (3) have no innate effects on stress responses. Here, we attempted to verify
Bed nucleus of stria terminalis
whether an artificial odor, which had no innate effect on predatory odor-induced stress, could
Predatory odor
alleviate stress if experienced in early life as a habitat odor. In the current study, we demonstrated
Norepinephrine
that the innate responses were changed to counteract stress following a postnatal experience.
c-fos
Moreover, we suggest that inhibitory circuits involved in stress-related neuronal networks and the
Anterior piriform cortex
concentrations of norepinephrine in the hippocampus may be crucial in alleviating stress induced
Olfactory bulb
by the predatory odor. Overall, these findings may be important for understanding the mechanisms involved in differential odor responses and also for the development of pharmacotherapeutic interventions that can alleviate stress in illnesses like PTSD. & 2015 Published by Elsevier B.V.
1.
stress, especially an exposure to a life-threatening event, can
Introduction
develop into chronic disorders such as post-traumatic stress Alleviating stress is a basic requirement for human welfare,
disorder (PTSD). Although definitive biomarkers for the devel-
as well as the welfare of laboratory animals. It is known that
opment of PTSD remain elusive, recent studies have shown
Abbreviations: 5-HT, cortex; BLA, EDTA,
serotonin; ACTH,
adrenocorticotropic hormone; ANOVA,
basolateral complex of amygdala; BST,
ethylenediaminetetraaceticacid; hinokitiol,
pituitary–adrenal gland; HPLC-ECD, coeruleus; NE, norepinephrine; OB,
analysis of variance; APC,
bed nucleus of stria terminalis; DHBA,
anterior piriform
3,4-dihydroxybenzylamine;
2-hydroxy-4-isopropyl-2,4,6-cycloheptatrien-1-one; HPA,
hypothalamo–
high performance liquid chromatography with an electrochemical detection system; LC, olfactory bulb; PFC,
prefrontal cortex; PTSD,
post-traumatic stress disorder; TMT,
locus
2,5-
Dihydro-2,4,5-trimethylthiazoline n Corresponding author. Fax: þ81 3 3973 8832. E-mail address: [email protected] (M. Matsukawa). http://dx.doi.org/10.1016/j.brainres.2015.11.020 0006-8993/& 2015 Published by Elsevier B.V.
Please cite this article as: Matsukawa, M., et al., Habitat odor can alleviate innate stress responses in mice. Brain Research (2015), http://dx.doi.org/10.1016/j.brainres.2015.11.020
181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197
BRES : 44566
2
198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257
brain research ] (]]]]) ]]]–]]]
that the hypothalamic–pituitary–adrenal (HPA) axis is involved (Liberzon et al., 1999; Söndergaard et al., 2004; Oosthuizen et al., 2005; Wilson et al., 2013; Zoladz and Diamond, 2013) and that the modulatory effects of some neurotransmitters are implicated in the disorder (Arora et al., 1993; Geracioti et al., 2001; Krystal and Neumeister, 2009; Southwick and Charney, 2012). In PTSD animal models, lower serotonin (5-HT) and elevated norepinephrine (NE) levels have recently been shown in some brain regions (Wilson et al., 2014). Hence, the regulation of such neurotransmitters has been the primary target of therapeutic intervention for PTSD treatment (Krystal and Neumeister, 2009). Odors from predatory animals are known to induce the innate stress response in prey animals. Exposure to a predator or predatory odor is used to create animal models of some neuropsychological disorders including anxiety, phobia and PTSD (Rosen et al., 2008; Staples, 2010; Zoladz et al., 2012). A synthetic compound mimicking the anal gland secretions of a red fox, 2,5-dihydro-2,4,5-trimethylthiazoline (TMT), is one of the most commonly used odors to induce a fear response and stress-like behavior in rodents (Vernet-Maury et al., 1984; Apfelbach et al., 2005; Fendt et al., 2005; Takahashi et al., 2008; Takahashi, 2014). In addition, several reports have shown that neonatal or pre-puberty exposure to TMT can exert a sex-related differential effect on fear-related behaviors (Toledo-Rodriguez and Sandi, 2007) and can Q2 decrease avoidance, immobility, and freezing during adulthood (Hacquemand et al., 2010). The bed nucleus of the stria terminalis (BST) is thought to be involved in these odorinduced stress-like responses (Fendt et al., 2003; Kobayakawa et al., 2007; Takahashi et al., 2014; Janitzky et al., 2015). Furthermore, TMT can increase the efflux of monoamines in the mouse brain (Hayley et al., 2001; Smith et al., 2006) and can activate the locus coeruleus (LC) from which noradrenergic fibers innervate the cerebral cortex, amygdala and hippocampus (Day et al., 2004; Curtis et al., 2012; Janitzky et al., 2015). TMT-induced stress-like responses in mice can be allayed by simultaneous presentation with rose odor (from Bulgarian rose oil) or hinokitiol odor (2-hydroxy-4-isopropyl-2,4,6-cycloheptatrien-1-one; a chemical constituent of woody oil from Thujopsis heartwood) but not in combination with caraway odor (S (þ)-carvone) (Matsukawa et al., 2011; Murakami et al., 2012). These studies have shown that there are at least three types of odor in nature: (1) odors that can innately induce stress-like behavior, such as predator odors like TMT; (2) odors that can innately alleviate predatory odor-induced stressrelated activities, such as rose and hinokitiol odor and (3) odors that have no effect, such as caraway odor. Hence, we hypothesized that postnatal experiences may have a modifying effect on the innate responses, leading to changes that may cause individual differences in odor response in adulthood. In the current study, we attempted to validate this hypothesis. In particular, a non-effective odor experienced as a habitat odor during the early postnatal period can alleviate TMT-induced stress in adulthood. To assess stress levels, we measured plasma concentrations of adrenocorticotropic hormone (ACTH), a biomarker of the HPA axis. Neuronal activation in the anterior piriform cortex (APC) and the BST was measured by assessing c-fos expression levels. We
also measured NE concentrations in the prefrontal cortex (PFC) and hippocampus. Previous studies of both these regions have shown an increase in NE levels following TMT exposure (Wilson et al., 2014).
2.
Results
2.1. Shredded newspaper odor could alleviate TMT-induced stress We used the artificial odor of shredded newspaper, which we anticipated to be an innate non-effective odor. First, we assessed whether the newspaper odor was non-effective by measuring plasma ACTH concentrations. Animals housed with standard laboratory bedding were used in this assessment. Exposure to TMT alone (T) or TMT in combination with newspaper odor (TN) significantly increased plasma ACTH levels compared with the odorless control (DDW) (one-way ANOVA: F (2, 15)¼ 8.237, Po0.01). Hence, the shredded newspaper odor was determined to be an innate non-effective odor for mice. In further experiments, we used shredded newspaper as bedding for mice during the 3-week lactational period and no bedding for 3 subsequent weeks. Exposure to TMT alone (T) significantly increased plasma ACTH concentrations but no changes were found when TMT was presented in combination with newspaper odor (TN) (one-way ANOVA: F (2, 15)¼ 29.15, Po0.001). This result shows that even the innate noneffective odor of shredded newspaper could alleviate the TMT-induced stress response if experienced as a habitat odor in early life (two-way ANOVA: bedding in early life, Po0.05, odor, Po0.05, interaction, Po0.05) (Fig. 1).
2.2. brain
Changes in the density of activated neurons in the
We previously reported that there are at least two distinct mechanisms involved in allaying TMT-induced stress-related activities. First, counteracting mechanisms that can directly suppress the neuronal activities in related brain regions, as shown in combination with rose odor and second, mechanisms in which the selective responses to TMT become indistinguishable, as shown using hinokitiol odor (Matsukawa et al., 2011; Murakami et al., 2012). We next assessed which mechanisms were involved in alleviating TMT-induced stress during simultaneous presentations of habitat odor, by counting c-fos expressing neurons in the APC and the BST. Activated neurons following the presentation of each odor, in the dorsal or ventrorostral APC (APCd and APCvr, respectively), are shown in Fig. 2. Although there was a significant increase in activation between each odor and its odorless control (DDW) in both APCd (one-way ANOVA: F (4, 55)¼ 18.45, Po0.001) and APCvr (one-way ANOVA: F (4, 55)¼ 18.51, Po0.001), there were no significant differences between early bedding vs odor presentation in the APCd (two-way ANOVA: bedding in early life, P¼ 0.873, odor, P¼ 0.633, interaction, P¼0.601) (Fig. 2a). In contrast, significantly fewer neurons were activated following presentation of TMT with newspaper odor (TN), for animals housed with newspaper bedding during the lactational period
Please cite this article as: Matsukawa, M., et al., Habitat odor can alleviate innate stress responses in mice. Brain Research (2015), http://dx.doi.org/10.1016/j.brainres.2015.11.020
258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 286 287 288 289 290 291 292 293 294 295 296 297 298 299 300 301 302 303 304 305 306 307 308 309 310 311 312 313 314 315 316 317
BRES : 44566 brain research ] (]]]]) ]]]–]]]
318 319 320 321 322 323 324 325 326 327 328 329 330 331 332 333 334 335 336 337 338 339 340 341 342 343 344 345 346 347 348 349 350 351 352 353 354 355 356 357 358 359 360 361 362 363 364 365 366 367 368 369 370 371 372 373 374 375 376 377
3
Fig. 1 – Concentration of plasma adrenocorticotropic hormone (ACTH) following each odor presentation, for the animals housed with standard laboratory bedding (open bars) and with shredded newspaper as bedding during their early life (gray bars). Asterisks denote statistically significant differences, in which * and ** represent Po0.05 and Po0.01, respectively, and n.s. means no significant differences. T, 2,5-dihydro-2,4,5-trimethylthiazoline (TMT) exposed alone; TN, TMT presented with newspaper odor.
(gray bar) in the APCvr (two-way ANOVA: bedding in early life, Po0.05, odor, Po0.05, interaction, Po0.05) (Fig. 2b). These results suggest that there are some regulatory mechanisms, which might be modulated by odors in the APCvr, may play a role in mediating stress-like behaviors. Fig. 3 shows the number of c-fos immunopositive cells in the medial and lateral BST (mBST and lBST, respectively). In mBST, there was a significant increase in c-fos expression following each odor presentation, except when TMT was presented with newspaper (TN), in animals housed with newspaper bedding in their early life (gray bar) (two-way ANOVA: bedding in early life, Po0.05; odor, Po0.01; interaction, Po0.05) (Fig. 3a). In contrast, there were no statistically significant differences in lBST c-fos expression after presentation of any of the odors (two-way ANOVA: bedding in early life, P ¼ 0.834; odor, P ¼0.470; interaction, P¼ 0.470) (Fig. 3b). The ratio of activated neurons in the mBST to the lBST, which was highly correlated with plasma ACTH levels in our previous study (Murakami et al., 2012), was higher following odor exposure (one-way ANOVA: F(4, 85)¼ 19.77, Po0.001).
2.3.
Changes in the concentration of NE
Subsequently, we measured the NE concentrations in the PFC and hippocampus of each odor presentation group. In the PFC, there was a statistically significant increase in NE levels following TMT alone (T) but not when TMT was combined with newspaper odor (TN) (one-way ANOVA: F (4, 25)¼ 3.134, Po0.05). These results did not reflect differences in bedding during the lactate period (standard laboratory bedding (open bar) compared with shredded newspaper bedding (gray bar)) (two-way ANOVA: bedding in early life, P¼ 0.825; odor, Po0.05; interaction, P¼0.2650) (Fig. 4a). In contrast, there was a
Fig. 2 – Change in the number of c-fos immunopositive neurons in APCd (a) and APCvr (b) following each odor presentation. Open bars show the animals housed with standard laboratory bedding and gray bars show the animals housed with shredded newspaper as bedding during their lactational period. Asterisks denote statistically significant differences, in which * and ** represent Po0.05 and Po0.01, respectively, and n.s. means no significant differences. T, 2,5-dihydro-2,4,5-trimethylthiazoline (TMT) exposed alone; TN, TMT presented with newspaper odor.
significant increase in NE concentration in the hippocampus following each odor presentation (one-way ANOVA: F (4, 25)¼ 3.033, Po0.05), except TMT in combination with newspaper odor (TN), in animals that were housed in newspaper bedding during the lactational period (gray bar, Fig. 4b) (two-way ANOVA: bedding in early life, Po0.05; odor, Po0.05; interaction, Po0.05). Note that the pattern of the NE level increases parallels the activity ratios in the BST, as well as the plasma ACTH concentrations (see Figs. 1, 3a and 4b). Therefore, higher NE concentrations in the hippocampus may have an important role in the development of stress responses.
3.
Discussion
3.1.
Habitat odor can allay predatory odor-induced stress
In the current study, we demonstrated that even an artificial odor, which was classified as a non-innate effective odor,
Please cite this article as: Matsukawa, M., et al., Habitat odor can alleviate innate stress responses in mice. Brain Research (2015), http://dx.doi.org/10.1016/j.brainres.2015.11.020
378 379 380 381 382 383 384 385 386 387 388 389 390 391 392 393 394 395 396 397 398 399 400 401 402 403 404 405 406 407 408 409 410 411 412 413 414 415 416 417 418 419 420 421 422 423 424 425 426 427 428 429 430 431 432 433 434 435 436 437
BRES : 44566
4
438 439 440 441 442 443 444 445 446 447 448 449 450 451 452 453 454 455 456 457 458 459 460 461 462 463 464 465 466 467 468 469 470 471 472 473 474 475 476 477 478 479 480 481 482 483 484 485 486 487 488 489 490 491 492 493 494 495 496 497
brain research ] (]]]]) ]]]–]]]
Fig. 3 – Number of c-fos positive cells in mBST (a) and lBST (b) and the ratios of activated neurons in the mBST to lBST (c) of each odor presented group. Open bars show the animals housed with the standard laboratory bedding and gray bar show the animals housed with shredded newspaper as bedding during their early period of life. Asterisks denote statistically significant differences, in which * and ** represent Po0.05 and Po0.01, respectively, and n.s. means no significant differences. T, 2,5-dihydro2,4,5-trimethylthiazoline (TMT) exposed alone; TN, TMT presented with newspaper odor.
could alleviate the predator odor-induced stress responses in adulthood, if the artificial odor was experienced as a habitat odor early in life. Postnatal experiences can change the innate responses that decide how to respond to odors and this may lead to individual differences in odor-induced stress relief. It is important to clarify the mechanisms underlying the development of individual odor sensitivities and also to develop odors that may alleviate stress for each individual.
3.2. Putative mechanisms to suppress stress-related neuronal activities Changes in the number of activated neurons in the APC and the BST were demonstrated in this study (Figs. 2 and 3). Combined with our previous findings (Matsukawa et al., 2011; Murakami et al., 2012), we conclude that habitat odor can alleviate predatory odor-induced stress-related neuronal responses by selectively suppressing the mBST, which seems to be the same mechanism used by rose odor to alleviate stress (Matsukawa et al., 2011). Although more experiments
Fig. 4 – Change in the norepinephrine (NE) concentration in the prefrontal cortex (a) and the hippocampus (b) following each odor presentation. Open bars show the animals housed with standard laboratory bedding and gray bar shows the animals housed with shredded newspaper as bedding during their lactational period. Asterisks denote statistically significant differences, in which * represent Po0.05, and n.s. means no significant differences. T, 2,5-dihydro-2,4,5trimethylthiazoline (TMT) exposed alone; TN, TMT presented with newspaper odor.
are needed, these findings provide a basis for the underlying mechanisms of selective suppression of stress-related neuronal circuits. In addition, APCvr, which was initially divided by morphological analyses (Ekstrand et al., 2001), has feedforward regulatory projections to the APCd and is thought to be important for olfactory information processing (Ishikawa et al., 2007; Sato et al., 2008). Taken together, these studies suggest that the olfactory information network from the olfactory bulb to the APCvr and/or the intrinsic suppressive circuits in the APCvr have an important role in the development of odor-induced stress-related responses.
3.3. NE concentrations in the hippocampus are correlated with stress responses In addition, we demonstrated changes in hippocampal NE concentrations following each odor presentation (Fig. 4). In this study, the patterns of change in plasma ACTH levels and neuronal activation of the BST paralleled the changes in hippocampal, but not PFC, NE concentrations. These data,
Please cite this article as: Matsukawa, M., et al., Habitat odor can alleviate innate stress responses in mice. Brain Research (2015), http://dx.doi.org/10.1016/j.brainres.2015.11.020
498 499 500 501 502 503 504 505 506 507 508 509 510 511 512 513 514 515 516 517 518 519 520 521 522 523 524 525 526 527 528 529 530 531 532 533 534 535 536 537 538 539 540 541 542 543 544 545 546 547 548 549 550 551 552 553 554 555 556 557
BRES : 44566 brain research ] (]]]]) ]]]–]]]
558 559 560 561 562 563 564 565 566 567 568 569 570 571 572 573 574 575 576 577 578 579 580 581 582 583 584 585 586 587 588 589 590 591 592 593 594 595 596 597 598 599 600 601 602 603 604 605 606 607 608 609 610 611 612 613 614 615 616 617
together with previous reports using PTSD model animals (Wilson et al., 2014; Janitzky et al., 2015), suggest that increased hippocampal NE concentrations are important in the stress response following exposure to a life-threatening event. Higher NE concentrations in the hippocampus have been shown to affect regulation of stress responses and learning under stress (de Kloet et al., 2005; Joëls et al., 2006; Ulrich-Lai and Herman, 2009). Moreover, it was also shown that hippocampal NE concentration, under stress conditions, affects memory consolidation via the amygdala. This particularly involves the basolateral complex of the amygdale (BLA), which is known to innervate excitatory glutamatergic connections to the anterior BST (Roozendaal et al., 2009; Galliot et al., 2010; Hubert and Muly, 2014). These findings suggest that increased concentrations of NE in the hippocampus may regulate the BST via the BLA to consolidate stress-related activities in the BST.
3.4.
Conclusions
Our present results confirm that early life environment can have a modifying effect on innate responses of odor and in the development of individual responses to odors in adulthood. The regulation of neuronal activities in the APCvr and BST and increased NE concentrations in the hippocampus may be important in TMT-induced stress responses, that can be counteracted by a habitat odor. Exposure to predatory odors is used in some psychiatric disease models (Rosen et al., 2008; Staples, 2010; Zoladz et al., 2012; Wilson et al., 2014; Janitzky et al., 2015), so our data could provide some understanding of the mechanisms involved in odor sensitivities and contribute to the development of pharmacotherapeutic interventions for stress-related disorders, including PTSD.
4.
Experimental procedures
4.1.
Animals
We used 6-week-old C57BL/6J mice in this study. Two types of bedding were used for housing: standard laboratory bedding for rodents and autoclaved, shredded newspaper. We used color-printed newspaper as a novel, artificial odor in this study because this artificial odor, not a natural odor, was supposed to be genetically naïve for laboratory animals. There were two groups of pregnant mice which were housed separately, 1 week prior to giving birth, with each of the bedding types. Pups were housed with their mothers during the 3-week lactation period in one of the two bedding types. After weaning, at 3 weeks of age, pups were housed in groups of three to five per cage (32 cm in length, 13 cm in width, and 12 cm in depth) without bedding (the bottom of the cage was 6 mm spaced grid-mesh flooring, from Natsume Seisakusho, Tokyo, Japan). The cages were set into a self-cleaning system, and were automatically washed twice a day with water (8:00 a.m. and 8:00 p.m.), for a further 3 weeks. Six animals were used for each odor presentation for each measuring of ACTH levels, c-fos expression and NE concentration. All animals were housed at 24 1C on a 12-h light/dark cycle (lights on at 8:00 a.m.) with ad libitum access to food and
5
water. Animal experiments and tissue sampling procedures were performed between 10:00 a.m. and 4:00 p.m. All experimental animal procedures followed the Guide for the Care and Use of Laboratory Animals of the National Institutes of Health (NIH; USA), and were approved by the animal experimental committee of Nihon University School of Medicine.
4.2.
Odor presentations
The odor of autoclaved shredded newspapers was infused into surgical cotton by burying the cotton into newspapers in a sealed plastic bag for 6 weeks. The odor strength of the infused cotton was measured using a handheld odor meter (Shinyei technology, Kobe, Japan) (Supplementary Table). We used 2,5-dihydro-2,4,5-trimethylthiazoline (TMT) (Phero tech, Delta, Canada) as the predator odor or filtered double distilled water (DDW) as an odorless control. Animals were individually placed in small cages (18 cm in length, 11 cm in width, and 10 cm in depth) without any bedding. According to our previous studies (Matsukawa et al., 2011; Murakami et al., 2012), each odor was presented following 5–10 min of habituation. Briefly, a piece of surgical cotton, approximately a 1 cm2, was placed in the cage and 200 μl of TMT (1.2 mM) or DDW solution was dropped onto it.
4.3. Measuring plasma adrenocorticotropic hormone (ACTH) concentrations Following 30 min of odor presentation, mice were euthanized by decapitation and whole blood was collected from the trunk using an ethylenediaminetetraacetic acid (EDTA)-containing (Sigma, St. Louis, MO, USA) syringe (n¼6 for each odorpresentation group). Plasma was stored at 80 1C. Adrenocorticotropic hormone (ACTH) was measured using an enzyme immunoassay kit (Peninsula Lab., San Carlos, CA, USA), as described in our previous studies (Matsukawa et al., 2011; Murakami et al., 2012).
4.4.
Measuring the neuronal activation
We used c-fos immunohistochemistry to evaluate neuronal activation in the anterior piriform cortex (APC) and the bed nucleus of stria terminalis (BST), after 30 min of odor presentation, as previously described (Matsukawa et al., 2011; Murakami et al., 2012). Briefly, animals were deeply anesthetized with 5% isoflurane and perfused with saline, followed by 4% paraformaldehyde in 0.1 M phosphate buffer (n ¼6 for each odor-presentation group). Coronal sections (50 mm thickness) were cut using a freezing microtome and every fifth section taken for c-fos immunohistochemistry using a polyclonal antibody against c-fos at a dilution of 1:10,000 (PAb-cfos; Sigma, St Louis, MO, USA). Photomicrographs from two (for APC) or three (for BST) distinct sections of each brain region were taken using light microscopy. Cell counting was carried out by the person who was unaware of odor presentation with the number of c-fos immunopositive cells counted per unit area of each photograph and confirmed using digital image analysis software, Image J (NIH, USA) (Supplementary Figure).
Please cite this article as: Matsukawa, M., et al., Habitat odor can alleviate innate stress responses in mice. Brain Research (2015), http://dx.doi.org/10.1016/j.brainres.2015.11.020
618 619 620 621 622 623 624 625 626 627 628 629 630 631 632 633 634 635 636 637 638 639 640 641 642 643 644 645 646 647 648 649 650 651 652 653 654 655 656 657 658 659 660 661 662 663 664 665 666 667 668 669 670 671 672 673 674 675 676 677
BRES : 44566
6
678 679 680 681 682 683 684 685 686 687 688 689 690 691 692 693 694 695 696 697 698 699 700 701 702 703 704 705 706 707 708 709 710 711 712 713 714 Q4 Q3 715 716 717 718 719 720 721 722 723 724 725 726 727 728 729 730 731 732 733 734 735 736 737
brain research ] (]]]]) ]]]–]]]
4.5.
Measuring norepinephrine (NE) concentrations
Standard high performance liquid chromatography with an electrochemical detection system (HPLC-ECD) was used to evaluate the NE concentrations in specific brain regions. Mice were euthanized by decapitation after 30 min of odor presentation (n¼ 6 for each odor-presentation group), the brains were quickly removed over ice and immersed in ice-chilled saline for several minutes. The prefrontal cortex and hippocampus were dissected out, frozen using liquid nitrogen and stored at 80 1C. Samples were homogenized in 180 μl of 0.1 N perchloric acid with 20 μl of 3,4-dihydroxybenzylamine (DHBA; Sigma) added as the internal standard. Following centrifugation for 10 min (15,000 rpm at 4 1C), 100 μl of supernatant was used for alumina oxide extraction. Briefly, 2 M Tris buffer (pH 8.6) was added to the samples and mixed by inversion for 10 min. After washing the sample mixture with DDW and eluting using 2% acetic acid, 20 μl of the eluate was injected into the HPLC-ECD with 0.65 V of an imposed potential on the working electrode vs. the Ag/AgCl reference electrode.
4.6.
Statistical analyses
Statistical analyses were performed using R language (R Foundation for Statistical Computing). Data were analyzed using one-way or two-way (bedding odor) analysis of variance (ANOVA) followed by post-hoc testing (Bonferroni's pairwise t test and Tukey's multiple comparisons test). Differences were considered to be significant when Po0.05. Data were expressed as the mean7standard error of the mean (SEM).
Acknowledgments This research was supported, in part, by a Grant-in-Aid for Scientific Research from the Japan Society for the Promotion of Science (to M.M.) and by a Nihon University Research Grant (to M.M.). Authors are grateful to the staff in the laboratory animals section (for help with animal research) and the biological chemistry section (for measurement of NE concentrations) at the medical research support center, Nihon University School of Medicine.
Appendix A.
Supplementary material
Supplementary data associated with this article can be found in the online version at http://dx.doi.org/10.1016/j.brainres. 2015.11.020.
references
Apfelbach, R., Blanchard, C.D., Blanchard, R.J., Hayes, R.A., McGregor, I.S., 2005. The effects of predator odors in mammalian prey species: a review of field and laboratory studies. Neurosci. Biobehav. Rev. 29, 1123–1144, http://dx.doi.org/ 10.1016/j.neubiorev.2005.05.005.
Arora, R.C., Fichtner, C.G., O’Connor, F., Crayton, J.W., 1993. Paroxetine binding in the blood platelets of post-traumatic stress disorder patients. Life Sci. 53, 919–928, http://dx.doi.org/ 10.1016/0024-3205(93)90444-8. Curtis, A.L., Leiser, S.C., Snyder, K., Valentino, R.J., 2012. Predator stress engages corticotropin-releasing factor and opioid systems to alter the operating mode of locus coeruleus norepinephrine neurons. Neuropharmacology 62, 1737–1745, http: //dx.doi.org/10.1016/j.neuropharm.2011.11.020. Day, H.E.W., Masini, C.V., Campeau, S., 2004. The pattern of brain c-fos mRNA induced by a component of fox odor, 2,5-dihydro2,4,5-Trimethylthiazoline (TMT), in rats, suggests both systemic and processive stress characteristics. Brain Res. 1025, 139–151, http://dx.doi.org/10.1016/j.brainres.2004.07.079. de Kloet, E.R., Joe¨ls, M., Holsboer, F., 2005. Stress and the brain: from adaptation to disease. Nat. Rev. Neurosci. 6, 463–475, http://dx.doi.org/10.1038/nrn1683. Ekstrand, J.J., Domroese, M.E., Johnson, D.M., Feig, S.L., Knodel, S. M., Behan, M., Haberly, L.B., 2001. A new subdivision of anterior piriform cortex and associated deep nucleus with novel features of interest for olfaction and epilepsy. J. Comp. Neurol. 434, 289–307. Fendt, M., Endres, T., Apfelbach, R., 2003. Temporary inactivation of the bed nucleus of the stria terminalis but not of the amygdala blocks freezing induced by trimethylthiazoline, a component of fox feces. J. Neurosci. 23, 23–28. Fendt, M., Endres, T., Lowry, C.A., Apfelbach, R., McGregor, I.S., 2005. TMT-induced autonomic and behavioral changes and the neural basis of its processing. Neurosci. Biobehav. Rev. 29, 1145–1156, http://dx.doi.org/10.1016/j.neubiorev.2005.04.018. Galliot, E., Levaillant, M., Beard, E., Millot, J.-L., Pourie´, G., 2010. Enhancement of spatial learning by predator odor in mice: involvement of amygdala and hippocampus. Neurobiol. Learn. Mem. 93, 196–202, http://dx.doi.org/10.1016/j.nlm.2009.09.011. Geracioti Jr, T.D., Baker, D.G., Ekhator, N.N., West, S.A., Hill, K.K., Bruce, A.B., et al., 2001. CSF norepinephrine concentrations in posttraumatic stress disorder. Am. J. Psychiatry 158, 1227–1230. Hacquemand, R., Pourie, G., Jacquot, L., Brand, G., 2010. Postnatal exposure to synthetic predator odor (TMT) induces quantitative modification in fear-related behaviors during adulthood without change in corticosterone levels. Behav. Brain Res. 215, 58–62, http://dx.doi.org/10.1016/j.bbr.2010.06.024. Hayley, S., Borowski, T., Merali, Z., Anisman, H., 2001. Central monoamine activity in genetically distinct strains of mice following a psychogenic stressor: effects of predator exposure. Brain Res. 892, 293–300. Hubert, G.W., Muly, E.C., 2014. Distribution of AMPA receptor subunit glur1 in the bed nucleus of the stria terminalis and effect of stress. Synapse 68, 194–201, http://dx.doi.org/10.1002/ syn.21729. Ishikawa, T., Sato, T., Shimizu, A., Tsutsui, K., de Curtis, M., Iijima, T., 2007. Odor-driven activity in the olfactory cortex of an in vitro isolated guinea pig whole brain with olfactory epithelium. J. Neurophysiol. 97, 670–679, http://dx.doi.org/ 10.1152/jn.01366.2005. Janitzky, K., D’Hanis, W., Kro¨ber, A., Schwegler, H., 2015. TMT predator odor activated neural circuit in C57BL/6J mice indicates TMT-stress as a suitable model for uncontrollable intense stress. Brain Res. 1599, 1–8, http://dx.doi.org/10.1016/j. brainres.2014.12.030. Joe¨ls, M., Pu, Z., Wiegert, O., Oitzl, M.S., Krugers, H.J., 2006. Learning under stress: how does it work? Trends Cogn. Sci. 10, 152–158, http://dx.doi.org/10.1016/j.tics.2006.02.002. Kobayakawa, K., Kobayakawa, R., Matsumoto, H., Oka, Y., Imai, T., Ikawa, M., et al., 2007. Innate versus learned odour processing in the mouse olfactory bulb. Nature 450, 503–508, http://dx. doi.org/10.1038/nature06281.
Please cite this article as: Matsukawa, M., et al., Habitat odor can alleviate innate stress responses in mice. Brain Research (2015), http://dx.doi.org/10.1016/j.brainres.2015.11.020
738 739 740 741 742 743 744 745 746 747 748 749 750 751 752 753 754 755 756 757 758 759 760 761 762 763 764 765 766 767 768 769 770 771 772 773 774 775 776 777 778 779 780 781 782 783 784 785 786 787 788 789 790 791 792 793 794 795 796 797
BRES : 44566 brain research ] (]]]]) ]]]–]]]
798 799 800 801 802 803 804 805 806 807 808 809 810 811 812 813 814 815 816 817 818 819 820 821 822 823 824 825 826 827 828 829 830 831 832 833 834 835 836
Krystal, J.H., Neumeister, A., 2009. Noradrenergic and serotonergic mechanisms in the neurobiology of posttraumatic stress disorder and resilience. Brain Res. 1293, 13–23, http://dx.doi. org/10.1016/j.brainres.2009.03.044. Liberzon, I., Abelson, J.L., Flagel, S.B., Raz, J., Young, E.A., 1999. Neuroendocrine and psychophysiologic responses in PTSD: a symptom provocation study. Neuropsychopharmacology 21, 40–50, http://dx.doi.org/10.1016/S0893-133X(98)00128-6. Matsukawa, M., Imada, M., Murakami, T., Aizawa, S., Sato, T., 2011. Rose odor can innately counteract predator odor. Brain Res. 1381, 117–123, http://dx.doi.org/10.1016/j.brainres.2011.01.053. Murakami, T., Matsukawa, M., Katsuyama, N., Imada, M., Aizawa, S., Sato, T., 2012. Stress-related activities induced by predator odor may become indistinguishable by hinokitiol odor. Neuroreport 23, 1071–1076, http://dx.doi.org/10.1097/WNR.0b013e32835b373b. Oosthuizen, F., Wegener, G., Harvey, B.H., 2005. Nitric oxide as inflammatory mediator in post-traumatic stress disorder (PTSD): evidence from an animal model. Neuropsychiatr. Dis. Treat. 1, 109–123. Roozendaal, B., McEwen, B.S., Chattarji, S., 2009. Stress, memory and the amygdala. Nat. Rev. Neurosci. 10, 423–433, http://dx. doi.org/10.1038/nrn2651. Rosen, J.B., Pagani, J.H., Rolla, K.L.G., Davis, C., 2008. Analysis of behavioral constraints and the neuroanatomy of fear to the predator odor trimethylthiazoline: a model for animal phobias. Neurosci. Biobehav. Rev. 32, 1267–1276, http://dx.doi.org/ 10.1016/j.neubiorev.2008.05.006. Sato, T., Hirono, J., Hamana, H., Ishikawa, T., Shimizu, A., Takashima, I., et al., 2008. Architecture of odor information processing in the olfactory system. Anat. Sci. Int. 83, 195–206, http://dx.doi.org/10.1111/j.1447-073x.2007.00215.x. Smith, D.G., Davis, R.J., Gehlert, D.R., Nomikos, G.G., 2006. Exposure to predator odor stress increases efflux of frontal cortex acetylcholine and monoamines in mice: comparisons with immobilization stress and reversal by chlordiazepoxide. Brain Res. 1114, 24–30, http://dx.doi.org/10.1016/j.brainres.2006.07.058. So¨ndergaard, H.P., Hansson, L.-O., Theorell, T., 2004. The inflammatory markers C-reactive protein and serum amyloid A in refugees with and without posttraumatic stress disorder. Clin. Chim. Acta 342, 93–98, http://dx.doi.org/10.1016/j.cccn.2003.12.019. Southwick, S.M., Charney, D.S., 2012. The science of resilience: implications for the prevention and treatment of depression. Science 338, 79–82, http://dx.doi.org/10.1126/science.1222942.
7
Staples, L.G., 2010. Predator odor avoidance as a rodent model of anxiety: learning-mediated consequences beyond the initial exposure. Neurobiol. Learn. Mem. 94, 435–445, http://dx.doi. org/10.1016/j.nlm.2010.09.009. Takahashi, L.K., 2014. Olfactory systems and neural circuits that modulate predator odor fear. Front. Behav. Neurosci. 8, 1–13, http://dx.doi.org/10.3389/fnbeh.2014.00072. Takahashi, L.K., Chan, M.M., Pilar, M.L., 2008. Predator odor fear conditioning: current perspectives and new directions. Neurosci. Biobehav. Rev. 32, 1218–1227, http://dx.doi.org/10.1016/j. neubiorev.2008.06.001. Toledo-Rodriguez, M., Sandi, C., 2007. Stress before puberty exerts a sex- and age-related impact on auditory and contextual fear conditioning in the rat. Neural Plast. 71203, 12, http://dx.doi. org/10.1155/2007/71203. Ulrich-Lai, Y.M., Herman, J.P., 2009. Neural regulation of endocrine and autonomic stress responses. Nat. Rev. Neurosci. 10, 397–409, http://dx.doi.org/10.1038/nrn2647. Vernet-Maury, E., Polak, E.H., Demael, A., 1984. Structure–activity relationship of stress-inducing odorants in the rat. J. Chem. Ecol. 10, 1007–1018, http://dx.doi.org/10.1007/BF00987509. Wilson, C.B., Ebenezer, P.J., McLaughlin, L.D., Francis, J., 2014. Predator exposure/psychosocial stress animal model of posttraumatic stress disorder modulates neurotransmitters in the rat hippocampus and prefrontal cortex. PLoS One 9, e89104, http://dx.doi.org/10.1371/journal.pone.0089104. Wilson, C.B., McLaughlin, L.D., Nair, A., Ebenezer, P.J., Dange, R., Francis, J., 2013. Inflammation and oxidative stress are elevated in the brain, blood, and adrenal glands during the progression of post-traumatic stress disorder in a predator exposure animal model. PLoS One 8, e76146, http://dx.doi.org/ 10.1371/journal.pone.0076146. Zoladz, P.R., Diamond, D.M., 2013. Current status on behavioral and biological markers of PTSD: a search for clarity in a conflicting literature. Neurosci. Biobehav. Rev. 37, 860–895, http://dx.doi.org/10.1016/j.neubiorev.2013.03.024. Zoladz, P.R., Fleshner, M., Diamond, D.M., 2012. Psychosocial animal model of PTSD produces a long-lasting traumatic memory, an increase in general anxiety and PTSD-like glucocorticoid abnormalities. Psychoneuroendocrinology 37, 1531–1545, http://dx.doi.org/10.1016/j.psyneuen.2012.02.007.
Please cite this article as: Matsukawa, M., et al., Habitat odor can alleviate innate stress responses in mice. Brain Research (2015), http://dx.doi.org/10.1016/j.brainres.2015.11.020
837 838 839 840 841 842 843 844 845 846 847 848 849 850 851 852 853 854 855 856 857 858 859 860 861 862 863 864 865 866 867 868 869 870 871 872 873 874
pp: 127ðcol:fig: : NILÞ
Model7 brain research ] (]]]]) ]]]–]]]
121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 Q1 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180
Available online at www.sciencedirect.com
www.elsevier.com/locate/brainres
Research report
Habitat odor can alleviate innate stress responses in mice Mutsumi Matsukawaa,n, Masato Imadaa, Shin Aizawaa, Takaaki Satob a
Division of Anatomical Science, Department of Functional Morphology, Nihon University School of Medicine, 30-1 Oyaguchi-Kamicho, Itabashi, Tokyo 173-8610, Japan b Biomedical Research Institute, National Institute of Advanced Industrial Science and Technology, 1-8-31 Midorigaoka, Ikeda, Osaka 563-8577, Japan
art i cle i nfo
ab st rac t
Article history:
Predatory odors, which can induce innate fear and stress responses in prey species, are frequently
Accepted 12 November 2015
used in the development of animal models for several psychiatric diseases including posttraumatic stress disorder (PTSD) following a life-threatening event. We have previously shown that odors can be divided into at least three types; odors that act as (1) innate stressors, (2) as
Keywords:
innate relaxants, or (3) have no innate effects on stress responses. Here, we attempted to verify
Bed nucleus of stria terminalis
whether an artificial odor, which had no innate effect on predatory odor-induced stress, could
Predatory odor
alleviate stress if experienced in early life as a habitat odor. In the current study, we demonstrated
Norepinephrine
that the innate responses were changed to counteract stress following a postnatal experience.
c-fos
Moreover, we suggest that inhibitory circuits involved in stress-related neuronal networks and the
Anterior piriform cortex
concentrations of norepinephrine in the hippocampus may be crucial in alleviating stress induced
Olfactory bulb
by the predatory odor. Overall, these findings may be important for understanding the mechanisms involved in differential odor responses and also for the development of pharmacotherapeutic interventions that can alleviate stress in illnesses like PTSD. & 2015 Published by Elsevier B.V.
1.
stress, especially an exposure to a life-threatening event, can
Introduction
develop into chronic disorders such as post-traumatic stress Alleviating stress is a basic requirement for human welfare,
disorder (PTSD). Although definitive biomarkers for the devel-
as well as the welfare of laboratory animals. It is known that
opment of PTSD remain elusive, recent studies have shown
Abbreviations: 5-HT, cortex; BLA, EDTA,
serotonin; ACTH,
adrenocorticotropic hormone; ANOVA,
basolateral complex of amygdala; BST,
ethylenediaminetetraaceticacid; hinokitiol,
pituitary–adrenal gland; HPLC-ECD, coeruleus; NE, norepinephrine; OB,
analysis of variance; APC,
bed nucleus of stria terminalis; DHBA,
anterior piriform
3,4-dihydroxybenzylamine;
2-hydroxy-4-isopropyl-2,4,6-cycloheptatrien-1-one; HPA,
hypothalamo–
high performance liquid chromatography with an electrochemical detection system; LC, olfactory bulb; PFC,
prefrontal cortex; PTSD,
post-traumatic stress disorder; TMT,
locus
2,5-
Dihydro-2,4,5-trimethylthiazoline n Corresponding author. Fax: þ81 3 3973 8832. E-mail address: [email protected] (M. Matsukawa). http://dx.doi.org/10.1016/j.brainres.2015.11.020 0006-8993/& 2015 Published by Elsevier B.V.
Please cite this article as: Matsukawa, M., et al., Habitat odor can alleviate innate stress responses in mice. Brain Research (2015), http://dx.doi.org/10.1016/j.brainres.2015.11.020
181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197
BRES : 44566
2
198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257
brain research ] (]]]]) ]]]–]]]
that the hypothalamic–pituitary–adrenal (HPA) axis is involved (Liberzon et al., 1999; Söndergaard et al., 2004; Oosthuizen et al., 2005; Wilson et al., 2013; Zoladz and Diamond, 2013) and that the modulatory effects of some neurotransmitters are implicated in the disorder (Arora et al., 1993; Geracioti et al., 2001; Krystal and Neumeister, 2009; Southwick and Charney, 2012). In PTSD animal models, lower serotonin (5-HT) and elevated norepinephrine (NE) levels have recently been shown in some brain regions (Wilson et al., 2014). Hence, the regulation of such neurotransmitters has been the primary target of therapeutic intervention for PTSD treatment (Krystal and Neumeister, 2009). Odors from predatory animals are known to induce the innate stress response in prey animals. Exposure to a predator or predatory odor is used to create animal models of some neuropsychological disorders including anxiety, phobia and PTSD (Rosen et al., 2008; Staples, 2010; Zoladz et al., 2012). A synthetic compound mimicking the anal gland secretions of a red fox, 2,5-dihydro-2,4,5-trimethylthiazoline (TMT), is one of the most commonly used odors to induce a fear response and stress-like behavior in rodents (Vernet-Maury et al., 1984; Apfelbach et al., 2005; Fendt et al., 2005; Takahashi et al., 2008; Takahashi, 2014). In addition, several reports have shown that neonatal or pre-puberty exposure to TMT can exert a sex-related differential effect on fear-related behaviors (Toledo-Rodriguez and Sandi, 2007) and can Q2 decrease avoidance, immobility, and freezing during adulthood (Hacquemand et al., 2010). The bed nucleus of the stria terminalis (BST) is thought to be involved in these odorinduced stress-like responses (Fendt et al., 2003; Kobayakawa et al., 2007; Takahashi et al., 2014; Janitzky et al., 2015). Furthermore, TMT can increase the efflux of monoamines in the mouse brain (Hayley et al., 2001; Smith et al., 2006) and can activate the locus coeruleus (LC) from which noradrenergic fibers innervate the cerebral cortex, amygdala and hippocampus (Day et al., 2004; Curtis et al., 2012; Janitzky et al., 2015). TMT-induced stress-like responses in mice can be allayed by simultaneous presentation with rose odor (from Bulgarian rose oil) or hinokitiol odor (2-hydroxy-4-isopropyl-2,4,6-cycloheptatrien-1-one; a chemical constituent of woody oil from Thujopsis heartwood) but not in combination with caraway odor (S (þ)-carvone) (Matsukawa et al., 2011; Murakami et al., 2012). These studies have shown that there are at least three types of odor in nature: (1) odors that can innately induce stress-like behavior, such as predator odors like TMT; (2) odors that can innately alleviate predatory odor-induced stressrelated activities, such as rose and hinokitiol odor and (3) odors that have no effect, such as caraway odor. Hence, we hypothesized that postnatal experiences may have a modifying effect on the innate responses, leading to changes that may cause individual differences in odor response in adulthood. In the current study, we attempted to validate this hypothesis. In particular, a non-effective odor experienced as a habitat odor during the early postnatal period can alleviate TMT-induced stress in adulthood. To assess stress levels, we measured plasma concentrations of adrenocorticotropic hormone (ACTH), a biomarker of the HPA axis. Neuronal activation in the anterior piriform cortex (APC) and the BST was measured by assessing c-fos expression levels. We
also measured NE concentrations in the prefrontal cortex (PFC) and hippocampus. Previous studies of both these regions have shown an increase in NE levels following TMT exposure (Wilson et al., 2014).
2.
Results
2.1. Shredded newspaper odor could alleviate TMT-induced stress We used the artificial odor of shredded newspaper, which we anticipated to be an innate non-effective odor. First, we assessed whether the newspaper odor was non-effective by measuring plasma ACTH concentrations. Animals housed with standard laboratory bedding were used in this assessment. Exposure to TMT alone (T) or TMT in combination with newspaper odor (TN) significantly increased plasma ACTH levels compared with the odorless control (DDW) (one-way ANOVA: F (2, 15)¼ 8.237, Po0.01). Hence, the shredded newspaper odor was determined to be an innate non-effective odor for mice. In further experiments, we used shredded newspaper as bedding for mice during the 3-week lactational period and no bedding for 3 subsequent weeks. Exposure to TMT alone (T) significantly increased plasma ACTH concentrations but no changes were found when TMT was presented in combination with newspaper odor (TN) (one-way ANOVA: F (2, 15)¼ 29.15, Po0.001). This result shows that even the innate noneffective odor of shredded newspaper could alleviate the TMT-induced stress response if experienced as a habitat odor in early life (two-way ANOVA: bedding in early life, Po0.05, odor, Po0.05, interaction, Po0.05) (Fig. 1).
2.2. brain
Changes in the density of activated neurons in the
We previously reported that there are at least two distinct mechanisms involved in allaying TMT-induced stress-related activities. First, counteracting mechanisms that can directly suppress the neuronal activities in related brain regions, as shown in combination with rose odor and second, mechanisms in which the selective responses to TMT become indistinguishable, as shown using hinokitiol odor (Matsukawa et al., 2011; Murakami et al., 2012). We next assessed which mechanisms were involved in alleviating TMT-induced stress during simultaneous presentations of habitat odor, by counting c-fos expressing neurons in the APC and the BST. Activated neurons following the presentation of each odor, in the dorsal or ventrorostral APC (APCd and APCvr, respectively), are shown in Fig. 2. Although there was a significant increase in activation between each odor and its odorless control (DDW) in both APCd (one-way ANOVA: F (4, 55)¼ 18.45, Po0.001) and APCvr (one-way ANOVA: F (4, 55)¼ 18.51, Po0.001), there were no significant differences between early bedding vs odor presentation in the APCd (two-way ANOVA: bedding in early life, P¼ 0.873, odor, P¼ 0.633, interaction, P¼0.601) (Fig. 2a). In contrast, significantly fewer neurons were activated following presentation of TMT with newspaper odor (TN), for animals housed with newspaper bedding during the lactational period
Please cite this article as: Matsukawa, M., et al., Habitat odor can alleviate innate stress responses in mice. Brain Research (2015), http://dx.doi.org/10.1016/j.brainres.2015.11.020
258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 286 287 288 289 290 291 292 293 294 295 296 297 298 299 300 301 302 303 304 305 306 307 308 309 310 311 312 313 314 315 316 317
BRES : 44566 brain research ] (]]]]) ]]]–]]]
318 319 320 321 322 323 324 325 326 327 328 329 330 331 332 333 334 335 336 337 338 339 340 341 342 343 344 345 346 347 348 349 350 351 352 353 354 355 356 357 358 359 360 361 362 363 364 365 366 367 368 369 370 371 372 373 374 375 376 377
3
Fig. 1 – Concentration of plasma adrenocorticotropic hormone (ACTH) following each odor presentation, for the animals housed with standard laboratory bedding (open bars) and with shredded newspaper as bedding during their early life (gray bars). Asterisks denote statistically significant differences, in which * and ** represent Po0.05 and Po0.01, respectively, and n.s. means no significant differences. T, 2,5-dihydro-2,4,5-trimethylthiazoline (TMT) exposed alone; TN, TMT presented with newspaper odor.
(gray bar) in the APCvr (two-way ANOVA: bedding in early life, Po0.05, odor, Po0.05, interaction, Po0.05) (Fig. 2b). These results suggest that there are some regulatory mechanisms, which might be modulated by odors in the APCvr, may play a role in mediating stress-like behaviors. Fig. 3 shows the number of c-fos immunopositive cells in the medial and lateral BST (mBST and lBST, respectively). In mBST, there was a significant increase in c-fos expression following each odor presentation, except when TMT was presented with newspaper (TN), in animals housed with newspaper bedding in their early life (gray bar) (two-way ANOVA: bedding in early life, Po0.05; odor, Po0.01; interaction, Po0.05) (Fig. 3a). In contrast, there were no statistically significant differences in lBST c-fos expression after presentation of any of the odors (two-way ANOVA: bedding in early life, P ¼ 0.834; odor, P ¼0.470; interaction, P¼ 0.470) (Fig. 3b). The ratio of activated neurons in the mBST to the lBST, which was highly correlated with plasma ACTH levels in our previous study (Murakami et al., 2012), was higher following odor exposure (one-way ANOVA: F(4, 85)¼ 19.77, Po0.001).
2.3.
Changes in the concentration of NE
Subsequently, we measured the NE concentrations in the PFC and hippocampus of each odor presentation group. In the PFC, there was a statistically significant increase in NE levels following TMT alone (T) but not when TMT was combined with newspaper odor (TN) (one-way ANOVA: F (4, 25)¼ 3.134, Po0.05). These results did not reflect differences in bedding during the lactate period (standard laboratory bedding (open bar) compared with shredded newspaper bedding (gray bar)) (two-way ANOVA: bedding in early life, P¼ 0.825; odor, Po0.05; interaction, P¼0.2650) (Fig. 4a). In contrast, there was a
Fig. 2 – Change in the number of c-fos immunopositive neurons in APCd (a) and APCvr (b) following each odor presentation. Open bars show the animals housed with standard laboratory bedding and gray bars show the animals housed with shredded newspaper as bedding during their lactational period. Asterisks denote statistically significant differences, in which * and ** represent Po0.05 and Po0.01, respectively, and n.s. means no significant differences. T, 2,5-dihydro-2,4,5-trimethylthiazoline (TMT) exposed alone; TN, TMT presented with newspaper odor.
significant increase in NE concentration in the hippocampus following each odor presentation (one-way ANOVA: F (4, 25)¼ 3.033, Po0.05), except TMT in combination with newspaper odor (TN), in animals that were housed in newspaper bedding during the lactational period (gray bar, Fig. 4b) (two-way ANOVA: bedding in early life, Po0.05; odor, Po0.05; interaction, Po0.05). Note that the pattern of the NE level increases parallels the activity ratios in the BST, as well as the plasma ACTH concentrations (see Figs. 1, 3a and 4b). Therefore, higher NE concentrations in the hippocampus may have an important role in the development of stress responses.
3.
Discussion
3.1.
Habitat odor can allay predatory odor-induced stress
In the current study, we demonstrated that even an artificial odor, which was classified as a non-innate effective odor,
Please cite this article as: Matsukawa, M., et al., Habitat odor can alleviate innate stress responses in mice. Brain Research (2015), http://dx.doi.org/10.1016/j.brainres.2015.11.020
378 379 380 381 382 383 384 385 386 387 388 389 390 391 392 393 394 395 396 397 398 399 400 401 402 403 404 405 406 407 408 409 410 411 412 413 414 415 416 417 418 419 420 421 422 423 424 425 426 427 428 429 430 431 432 433 434 435 436 437
BRES : 44566
4
438 439 440 441 442 443 444 445 446 447 448 449 450 451 452 453 454 455 456 457 458 459 460 461 462 463 464 465 466 467 468 469 470 471 472 473 474 475 476 477 478 479 480 481 482 483 484 485 486 487 488 489 490 491 492 493 494 495 496 497
brain research ] (]]]]) ]]]–]]]
Fig. 3 – Number of c-fos positive cells in mBST (a) and lBST (b) and the ratios of activated neurons in the mBST to lBST (c) of each odor presented group. Open bars show the animals housed with the standard laboratory bedding and gray bar show the animals housed with shredded newspaper as bedding during their early period of life. Asterisks denote statistically significant differences, in which * and ** represent Po0.05 and Po0.01, respectively, and n.s. means no significant differences. T, 2,5-dihydro2,4,5-trimethylthiazoline (TMT) exposed alone; TN, TMT presented with newspaper odor.
could alleviate the predator odor-induced stress responses in adulthood, if the artificial odor was experienced as a habitat odor early in life. Postnatal experiences can change the innate responses that decide how to respond to odors and this may lead to individual differences in odor-induced stress relief. It is important to clarify the mechanisms underlying the development of individual odor sensitivities and also to develop odors that may alleviate stress for each individual.
3.2. Putative mechanisms to suppress stress-related neuronal activities Changes in the number of activated neurons in the APC and the BST were demonstrated in this study (Figs. 2 and 3). Combined with our previous findings (Matsukawa et al., 2011; Murakami et al., 2012), we conclude that habitat odor can alleviate predatory odor-induced stress-related neuronal responses by selectively suppressing the mBST, which seems to be the same mechanism used by rose odor to alleviate stress (Matsukawa et al., 2011). Although more experiments
Fig. 4 – Change in the norepinephrine (NE) concentration in the prefrontal cortex (a) and the hippocampus (b) following each odor presentation. Open bars show the animals housed with standard laboratory bedding and gray bar shows the animals housed with shredded newspaper as bedding during their lactational period. Asterisks denote statistically significant differences, in which * represent Po0.05, and n.s. means no significant differences. T, 2,5-dihydro-2,4,5trimethylthiazoline (TMT) exposed alone; TN, TMT presented with newspaper odor.
are needed, these findings provide a basis for the underlying mechanisms of selective suppression of stress-related neuronal circuits. In addition, APCvr, which was initially divided by morphological analyses (Ekstrand et al., 2001), has feedforward regulatory projections to the APCd and is thought to be important for olfactory information processing (Ishikawa et al., 2007; Sato et al., 2008). Taken together, these studies suggest that the olfactory information network from the olfactory bulb to the APCvr and/or the intrinsic suppressive circuits in the APCvr have an important role in the development of odor-induced stress-related responses.
3.3. NE concentrations in the hippocampus are correlated with stress responses In addition, we demonstrated changes in hippocampal NE concentrations following each odor presentation (Fig. 4). In this study, the patterns of change in plasma ACTH levels and neuronal activation of the BST paralleled the changes in hippocampal, but not PFC, NE concentrations. These data,
Please cite this article as: Matsukawa, M., et al., Habitat odor can alleviate innate stress responses in mice. Brain Research (2015), http://dx.doi.org/10.1016/j.brainres.2015.11.020
498 499 500 501 502 503 504 505 506 507 508 509 510 511 512 513 514 515 516 517 518 519 520 521 522 523 524 525 526 527 528 529 530 531 532 533 534 535 536 537 538 539 540 541 542 543 544 545 546 547 548 549 550 551 552 553 554 555 556 557
BRES : 44566 brain research ] (]]]]) ]]]–]]]
558 559 560 561 562 563 564 565 566 567 568 569 570 571 572 573 574 575 576 577 578 579 580 581 582 583 584 585 586 587 588 589 590 591 592 593 594 595 596 597 598 599 600 601 602 603 604 605 606 607 608 609 610 611 612 613 614 615 616 617
together with previous reports using PTSD model animals (Wilson et al., 2014; Janitzky et al., 2015), suggest that increased hippocampal NE concentrations are important in the stress response following exposure to a life-threatening event. Higher NE concentrations in the hippocampus have been shown to affect regulation of stress responses and learning under stress (de Kloet et al., 2005; Joëls et al., 2006; Ulrich-Lai and Herman, 2009). Moreover, it was also shown that hippocampal NE concentration, under stress conditions, affects memory consolidation via the amygdala. This particularly involves the basolateral complex of the amygdale (BLA), which is known to innervate excitatory glutamatergic connections to the anterior BST (Roozendaal et al., 2009; Galliot et al., 2010; Hubert and Muly, 2014). These findings suggest that increased concentrations of NE in the hippocampus may regulate the BST via the BLA to consolidate stress-related activities in the BST.
3.4.
Conclusions
Our present results confirm that early life environment can have a modifying effect on innate responses of odor and in the development of individual responses to odors in adulthood. The regulation of neuronal activities in the APCvr and BST and increased NE concentrations in the hippocampus may be important in TMT-induced stress responses, that can be counteracted by a habitat odor. Exposure to predatory odors is used in some psychiatric disease models (Rosen et al., 2008; Staples, 2010; Zoladz et al., 2012; Wilson et al., 2014; Janitzky et al., 2015), so our data could provide some understanding of the mechanisms involved in odor sensitivities and contribute to the development of pharmacotherapeutic interventions for stress-related disorders, including PTSD.
4.
Experimental procedures
4.1.
Animals
We used 6-week-old C57BL/6J mice in this study. Two types of bedding were used for housing: standard laboratory bedding for rodents and autoclaved, shredded newspaper. We used color-printed newspaper as a novel, artificial odor in this study because this artificial odor, not a natural odor, was supposed to be genetically naïve for laboratory animals. There were two groups of pregnant mice which were housed separately, 1 week prior to giving birth, with each of the bedding types. Pups were housed with their mothers during the 3-week lactation period in one of the two bedding types. After weaning, at 3 weeks of age, pups were housed in groups of three to five per cage (32 cm in length, 13 cm in width, and 12 cm in depth) without bedding (the bottom of the cage was 6 mm spaced grid-mesh flooring, from Natsume Seisakusho, Tokyo, Japan). The cages were set into a self-cleaning system, and were automatically washed twice a day with water (8:00 a.m. and 8:00 p.m.), for a further 3 weeks. Six animals were used for each odor presentation for each measuring of ACTH levels, c-fos expression and NE concentration. All animals were housed at 24 1C on a 12-h light/dark cycle (lights on at 8:00 a.m.) with ad libitum access to food and
5
water. Animal experiments and tissue sampling procedures were performed between 10:00 a.m. and 4:00 p.m. All experimental animal procedures followed the Guide for the Care and Use of Laboratory Animals of the National Institutes of Health (NIH; USA), and were approved by the animal experimental committee of Nihon University School of Medicine.
4.2.
Odor presentations
The odor of autoclaved shredded newspapers was infused into surgical cotton by burying the cotton into newspapers in a sealed plastic bag for 6 weeks. The odor strength of the infused cotton was measured using a handheld odor meter (Shinyei technology, Kobe, Japan) (Supplementary Table). We used 2,5-dihydro-2,4,5-trimethylthiazoline (TMT) (Phero tech, Delta, Canada) as the predator odor or filtered double distilled water (DDW) as an odorless control. Animals were individually placed in small cages (18 cm in length, 11 cm in width, and 10 cm in depth) without any bedding. According to our previous studies (Matsukawa et al., 2011; Murakami et al., 2012), each odor was presented following 5–10 min of habituation. Briefly, a piece of surgical cotton, approximately a 1 cm2, was placed in the cage and 200 μl of TMT (1.2 mM) or DDW solution was dropped onto it.
4.3. Measuring plasma adrenocorticotropic hormone (ACTH) concentrations Following 30 min of odor presentation, mice were euthanized by decapitation and whole blood was collected from the trunk using an ethylenediaminetetraacetic acid (EDTA)-containing (Sigma, St. Louis, MO, USA) syringe (n¼6 for each odorpresentation group). Plasma was stored at 80 1C. Adrenocorticotropic hormone (ACTH) was measured using an enzyme immunoassay kit (Peninsula Lab., San Carlos, CA, USA), as described in our previous studies (Matsukawa et al., 2011; Murakami et al., 2012).
4.4.
Measuring the neuronal activation
We used c-fos immunohistochemistry to evaluate neuronal activation in the anterior piriform cortex (APC) and the bed nucleus of stria terminalis (BST), after 30 min of odor presentation, as previously described (Matsukawa et al., 2011; Murakami et al., 2012). Briefly, animals were deeply anesthetized with 5% isoflurane and perfused with saline, followed by 4% paraformaldehyde in 0.1 M phosphate buffer (n ¼6 for each odor-presentation group). Coronal sections (50 mm thickness) were cut using a freezing microtome and every fifth section taken for c-fos immunohistochemistry using a polyclonal antibody against c-fos at a dilution of 1:10,000 (PAb-cfos; Sigma, St Louis, MO, USA). Photomicrographs from two (for APC) or three (for BST) distinct sections of each brain region were taken using light microscopy. Cell counting was carried out by the person who was unaware of odor presentation with the number of c-fos immunopositive cells counted per unit area of each photograph and confirmed using digital image analysis software, Image J (NIH, USA) (Supplementary Figure).
Please cite this article as: Matsukawa, M., et al., Habitat odor can alleviate innate stress responses in mice. Brain Research (2015), http://dx.doi.org/10.1016/j.brainres.2015.11.020
618 619 620 621 622 623 624 625 626 627 628 629 630 631 632 633 634 635 636 637 638 639 640 641 642 643 644 645 646 647 648 649 650 651 652 653 654 655 656 657 658 659 660 661 662 663 664 665 666 667 668 669 670 671 672 673 674 675 676 677
BRES : 44566
6
678 679 680 681 682 683 684 685 686 687 688 689 690 691 692 693 694 695 696 697 698 699 700 701 702 703 704 705 706 707 708 709 710 711 712 713 714 Q4 Q3 715 716 717 718 719 720 721 722 723 724 725 726 727 728 729 730 731 732 733 734 735 736 737
brain research ] (]]]]) ]]]–]]]
4.5.
Measuring norepinephrine (NE) concentrations
Standard high performance liquid chromatography with an electrochemical detection system (HPLC-ECD) was used to evaluate the NE concentrations in specific brain regions. Mice were euthanized by decapitation after 30 min of odor presentation (n¼ 6 for each odor-presentation group), the brains were quickly removed over ice and immersed in ice-chilled saline for several minutes. The prefrontal cortex and hippocampus were dissected out, frozen using liquid nitrogen and stored at 80 1C. Samples were homogenized in 180 μl of 0.1 N perchloric acid with 20 μl of 3,4-dihydroxybenzylamine (DHBA; Sigma) added as the internal standard. Following centrifugation for 10 min (15,000 rpm at 4 1C), 100 μl of supernatant was used for alumina oxide extraction. Briefly, 2 M Tris buffer (pH 8.6) was added to the samples and mixed by inversion for 10 min. After washing the sample mixture with DDW and eluting using 2% acetic acid, 20 μl of the eluate was injected into the HPLC-ECD with 0.65 V of an imposed potential on the working electrode vs. the Ag/AgCl reference electrode.
4.6.
Statistical analyses
Statistical analyses were performed using R language (R Foundation for Statistical Computing). Data were analyzed using one-way or two-way (bedding odor) analysis of variance (ANOVA) followed by post-hoc testing (Bonferroni's pairwise t test and Tukey's multiple comparisons test). Differences were considered to be significant when Po0.05. Data were expressed as the mean7standard error of the mean (SEM).
Acknowledgments This research was supported, in part, by a Grant-in-Aid for Scientific Research from the Japan Society for the Promotion of Science (to M.M.) and by a Nihon University Research Grant (to M.M.). Authors are grateful to the staff in the laboratory animals section (for help with animal research) and the biological chemistry section (for measurement of NE concentrations) at the medical research support center, Nihon University School of Medicine.
Appendix A.
Supplementary material
Supplementary data associated with this article can be found in the online version at http://dx.doi.org/10.1016/j.brainres. 2015.11.020.
references
Apfelbach, R., Blanchard, C.D., Blanchard, R.J., Hayes, R.A., McGregor, I.S., 2005. The effects of predator odors in mammalian prey species: a review of field and laboratory studies. Neurosci. Biobehav. Rev. 29, 1123–1144, http://dx.doi.org/ 10.1016/j.neubiorev.2005.05.005.
Arora, R.C., Fichtner, C.G., O’Connor, F., Crayton, J.W., 1993. Paroxetine binding in the blood platelets of post-traumatic stress disorder patients. Life Sci. 53, 919–928, http://dx.doi.org/ 10.1016/0024-3205(93)90444-8. Curtis, A.L., Leiser, S.C., Snyder, K., Valentino, R.J., 2012. Predator stress engages corticotropin-releasing factor and opioid systems to alter the operating mode of locus coeruleus norepinephrine neurons. Neuropharmacology 62, 1737–1745, http: //dx.doi.org/10.1016/j.neuropharm.2011.11.020. Day, H.E.W., Masini, C.V., Campeau, S., 2004. The pattern of brain c-fos mRNA induced by a component of fox odor, 2,5-dihydro2,4,5-Trimethylthiazoline (TMT), in rats, suggests both systemic and processive stress characteristics. Brain Res. 1025, 139–151, http://dx.doi.org/10.1016/j.brainres.2004.07.079. de Kloet, E.R., Joe¨ls, M., Holsboer, F., 2005. Stress and the brain: from adaptation to disease. Nat. Rev. Neurosci. 6, 463–475, http://dx.doi.org/10.1038/nrn1683. Ekstrand, J.J., Domroese, M.E., Johnson, D.M., Feig, S.L., Knodel, S. M., Behan, M., Haberly, L.B., 2001. A new subdivision of anterior piriform cortex and associated deep nucleus with novel features of interest for olfaction and epilepsy. J. Comp. Neurol. 434, 289–307. Fendt, M., Endres, T., Apfelbach, R., 2003. Temporary inactivation of the bed nucleus of the stria terminalis but not of the amygdala blocks freezing induced by trimethylthiazoline, a component of fox feces. J. Neurosci. 23, 23–28. Fendt, M., Endres, T., Lowry, C.A., Apfelbach, R., McGregor, I.S., 2005. TMT-induced autonomic and behavioral changes and the neural basis of its processing. Neurosci. Biobehav. Rev. 29, 1145–1156, http://dx.doi.org/10.1016/j.neubiorev.2005.04.018. Galliot, E., Levaillant, M., Beard, E., Millot, J.-L., Pourie´, G., 2010. Enhancement of spatial learning by predator odor in mice: involvement of amygdala and hippocampus. Neurobiol. Learn. Mem. 93, 196–202, http://dx.doi.org/10.1016/j.nlm.2009.09.011. Geracioti Jr, T.D., Baker, D.G., Ekhator, N.N., West, S.A., Hill, K.K., Bruce, A.B., et al., 2001. CSF norepinephrine concentrations in posttraumatic stress disorder. Am. J. Psychiatry 158, 1227–1230. Hacquemand, R., Pourie, G., Jacquot, L., Brand, G., 2010. Postnatal exposure to synthetic predator odor (TMT) induces quantitative modification in fear-related behaviors during adulthood without change in corticosterone levels. Behav. Brain Res. 215, 58–62, http://dx.doi.org/10.1016/j.bbr.2010.06.024. Hayley, S., Borowski, T., Merali, Z., Anisman, H., 2001. Central monoamine activity in genetically distinct strains of mice following a psychogenic stressor: effects of predator exposure. Brain Res. 892, 293–300. Hubert, G.W., Muly, E.C., 2014. Distribution of AMPA receptor subunit glur1 in the bed nucleus of the stria terminalis and effect of stress. Synapse 68, 194–201, http://dx.doi.org/10.1002/ syn.21729. Ishikawa, T., Sato, T., Shimizu, A., Tsutsui, K., de Curtis, M., Iijima, T., 2007. Odor-driven activity in the olfactory cortex of an in vitro isolated guinea pig whole brain with olfactory epithelium. J. Neurophysiol. 97, 670–679, http://dx.doi.org/ 10.1152/jn.01366.2005. Janitzky, K., D’Hanis, W., Kro¨ber, A., Schwegler, H., 2015. TMT predator odor activated neural circuit in C57BL/6J mice indicates TMT-stress as a suitable model for uncontrollable intense stress. Brain Res. 1599, 1–8, http://dx.doi.org/10.1016/j. brainres.2014.12.030. Joe¨ls, M., Pu, Z., Wiegert, O., Oitzl, M.S., Krugers, H.J., 2006. Learning under stress: how does it work? Trends Cogn. Sci. 10, 152–158, http://dx.doi.org/10.1016/j.tics.2006.02.002. Kobayakawa, K., Kobayakawa, R., Matsumoto, H., Oka, Y., Imai, T., Ikawa, M., et al., 2007. Innate versus learned odour processing in the mouse olfactory bulb. Nature 450, 503–508, http://dx. doi.org/10.1038/nature06281.
Please cite this article as: Matsukawa, M., et al., Habitat odor can alleviate innate stress responses in mice. Brain Research (2015), http://dx.doi.org/10.1016/j.brainres.2015.11.020
738 739 740 741 742 743 744 745 746 747 748 749 750 751 752 753 754 755 756 757 758 759 760 761 762 763 764 765 766 767 768 769 770 771 772 773 774 775 776 777 778 779 780 781 782 783 784 785 786 787 788 789 790 791 792 793 794 795 796 797
BRES : 44566 brain research ] (]]]]) ]]]–]]]
798 799 800 801 802 803 804 805 806 807 808 809 810 811 812 813 814 815 816 817 818 819 820 821 822 823 824 825 826 827 828 829 830 831 832 833 834 835 836
Krystal, J.H., Neumeister, A., 2009. Noradrenergic and serotonergic mechanisms in the neurobiology of posttraumatic stress disorder and resilience. Brain Res. 1293, 13–23, http://dx.doi. org/10.1016/j.brainres.2009.03.044. Liberzon, I., Abelson, J.L., Flagel, S.B., Raz, J., Young, E.A., 1999. Neuroendocrine and psychophysiologic responses in PTSD: a symptom provocation study. Neuropsychopharmacology 21, 40–50, http://dx.doi.org/10.1016/S0893-133X(98)00128-6. Matsukawa, M., Imada, M., Murakami, T., Aizawa, S., Sato, T., 2011. Rose odor can innately counteract predator odor. Brain Res. 1381, 117–123, http://dx.doi.org/10.1016/j.brainres.2011.01.053. Murakami, T., Matsukawa, M., Katsuyama, N., Imada, M., Aizawa, S., Sato, T., 2012. Stress-related activities induced by predator odor may become indistinguishable by hinokitiol odor. Neuroreport 23, 1071–1076, http://dx.doi.org/10.1097/WNR.0b013e32835b373b. Oosthuizen, F., Wegener, G., Harvey, B.H., 2005. Nitric oxide as inflammatory mediator in post-traumatic stress disorder (PTSD): evidence from an animal model. Neuropsychiatr. Dis. Treat. 1, 109–123. Roozendaal, B., McEwen, B.S., Chattarji, S., 2009. Stress, memory and the amygdala. Nat. Rev. Neurosci. 10, 423–433, http://dx. doi.org/10.1038/nrn2651. Rosen, J.B., Pagani, J.H., Rolla, K.L.G., Davis, C., 2008. Analysis of behavioral constraints and the neuroanatomy of fear to the predator odor trimethylthiazoline: a model for animal phobias. Neurosci. Biobehav. Rev. 32, 1267–1276, http://dx.doi.org/ 10.1016/j.neubiorev.2008.05.006. Sato, T., Hirono, J., Hamana, H., Ishikawa, T., Shimizu, A., Takashima, I., et al., 2008. Architecture of odor information processing in the olfactory system. Anat. Sci. Int. 83, 195–206, http://dx.doi.org/10.1111/j.1447-073x.2007.00215.x. Smith, D.G., Davis, R.J., Gehlert, D.R., Nomikos, G.G., 2006. Exposure to predator odor stress increases efflux of frontal cortex acetylcholine and monoamines in mice: comparisons with immobilization stress and reversal by chlordiazepoxide. Brain Res. 1114, 24–30, http://dx.doi.org/10.1016/j.brainres.2006.07.058. So¨ndergaard, H.P., Hansson, L.-O., Theorell, T., 2004. The inflammatory markers C-reactive protein and serum amyloid A in refugees with and without posttraumatic stress disorder. Clin. Chim. Acta 342, 93–98, http://dx.doi.org/10.1016/j.cccn.2003.12.019. Southwick, S.M., Charney, D.S., 2012. The science of resilience: implications for the prevention and treatment of depression. Science 338, 79–82, http://dx.doi.org/10.1126/science.1222942.
7
Staples, L.G., 2010. Predator odor avoidance as a rodent model of anxiety: learning-mediated consequences beyond the initial exposure. Neurobiol. Learn. Mem. 94, 435–445, http://dx.doi. org/10.1016/j.nlm.2010.09.009. Takahashi, L.K., 2014. Olfactory systems and neural circuits that modulate predator odor fear. Front. Behav. Neurosci. 8, 1–13, http://dx.doi.org/10.3389/fnbeh.2014.00072. Takahashi, L.K., Chan, M.M., Pilar, M.L., 2008. Predator odor fear conditioning: current perspectives and new directions. Neurosci. Biobehav. Rev. 32, 1218–1227, http://dx.doi.org/10.1016/j. neubiorev.2008.06.001. Toledo-Rodriguez, M., Sandi, C., 2007. Stress before puberty exerts a sex- and age-related impact on auditory and contextual fear conditioning in the rat. Neural Plast. 71203, 12, http://dx.doi. org/10.1155/2007/71203. Ulrich-Lai, Y.M., Herman, J.P., 2009. Neural regulation of endocrine and autonomic stress responses. Nat. Rev. Neurosci. 10, 397–409, http://dx.doi.org/10.1038/nrn2647. Vernet-Maury, E., Polak, E.H., Demael, A., 1984. Structure–activity relationship of stress-inducing odorants in the rat. J. Chem. Ecol. 10, 1007–1018, http://dx.doi.org/10.1007/BF00987509. Wilson, C.B., Ebenezer, P.J., McLaughlin, L.D., Francis, J., 2014. Predator exposure/psychosocial stress animal model of posttraumatic stress disorder modulates neurotransmitters in the rat hippocampus and prefrontal cortex. PLoS One 9, e89104, http://dx.doi.org/10.1371/journal.pone.0089104. Wilson, C.B., McLaughlin, L.D., Nair, A., Ebenezer, P.J., Dange, R., Francis, J., 2013. Inflammation and oxidative stress are elevated in the brain, blood, and adrenal glands during the progression of post-traumatic stress disorder in a predator exposure animal model. PLoS One 8, e76146, http://dx.doi.org/ 10.1371/journal.pone.0076146. Zoladz, P.R., Diamond, D.M., 2013. Current status on behavioral and biological markers of PTSD: a search for clarity in a conflicting literature. Neurosci. Biobehav. Rev. 37, 860–895, http://dx.doi.org/10.1016/j.neubiorev.2013.03.024. Zoladz, P.R., Fleshner, M., Diamond, D.M., 2012. Psychosocial animal model of PTSD produces a long-lasting traumatic memory, an increase in general anxiety and PTSD-like glucocorticoid abnormalities. Psychoneuroendocrinology 37, 1531–1545, http://dx.doi.org/10.1016/j.psyneuen.2012.02.007.
Please cite this article as: Matsukawa, M., et al., Habitat odor can alleviate innate stress responses in mice. Brain Research (2015), http://dx.doi.org/10.1016/j.brainres.2015.11.020
837 838 839 840 841 842 843 844 845 846 847 848 849 850 851 852 853 854 855 856 857 858 859 860 861 862 863 864 865 866 867 868 869 870 871 872 873 874