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Differential effects of two corticotropin-releasing factor antagonists on conditioned defeat in male Syrian hamsters (Mesocricetus auratus)
Brain Research 846 Ž1999. 122–128 www.elsevier.comrlocaterbres
Research report
Differential effects of two corticotropin-releasing factor antagonists on conditioned defeat in male Syrian hamsters ŽMesocricetus auratus . Aaron M. Jasnow, Matia C. Banks, Elizabeth C. Owens, Kim L. Huhman
)
Laboratory of BehaÕioral Neuroscience, Department of Psychology, Georgia State UniÕersity, Atlanta, GA 30303, USA Accepted 17 August 1999
Abstract The purpose of the present study was to determine whether corticotropin-releasing factor ŽCRF. is involved in mediating the expression of conditioned defeat in male Syrian hamsters. The present study examined the effects of two different competitive CRF receptor antagonists on the expression of conditioned defeat. Specifically, Experiment 1 examined whether peripheral administration of CP-154,526, a specific non-peptide CRF1 receptor antagonist, would reduce the expression of conditioned defeat. Experiment 2 examined whether D-Phe CRFŽ12 – 41. , a nonspecific CRF1rCRF2 receptor antagonist, infused directly into the brain, would reduce the expression of conditioned defeat. The results revealed that i.p. injections of CP-154,526 did not reduce the expression of conditioned defeat, whereas i.c.v. injections of D-Phe CRFŽ12 – 41. successfully reduced the expression of conditioned defeat. The duration of submissiverdefensive behaviors in hamsters that received the high dose of D-Phe CRFŽ12 – 41. was significantly less than that exhibited by animals that received a vehicle control. The present data suggest that central CRF may be involved in mediating the expression of conditioned defeat and other behavioral responses to stressful stimuli. q 1999 Elsevier Science B.V. All rights reserved. Keywords: Corticotropin-releasing factor; Social stress; Aggression; Agonistic behavior
1. Introduction Many animal species are exposed to social stressors during their lifetime. These stressors may include territorial conflict, competition for food and competition between males for access to females. In these conflicts there is usually a winner and a loser. Defeated animals display an increased activation of the hypothalamic–pituitary–adrenal ŽHPA. axis as evidenced by increased release of adrenocorticotropin ŽACTH., b-endorphin, cortisol and corticosterone. Dominant animals, however, display no such hormonal stress response w17–19x. Several lines of evidence suggest that social defeat also results in lasting autonomic and behavioral changes. Following a brief agonistic encounter, defeated animals exhibit increased blood pressure and heart rate and have compromised immune function w4,5,29x. The behavioral changes that may occur following defeat include decreased reproductive behavior, decreased food and water intake, decreased exploratory behavior, increased anxiety and decreased aggressive behavior ) Corresponding [email protected]
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w2,15,33,34x. These data suggest that losing a fight results in a suite of physiological, behavioral and autonomic changes, some of which may become deleterious to the defeated animal. Corticotropin-releasing factor ŽCRF. traditionally has been considered the primary neurohormone mediating the activity of the HPA axis; however, the localization of CRF-containing cell bodies and CRF receptors in extrahypothalamic brain areas suggests that CRF also may be involved in mediating autonomic and behavioral responses to stressors w6,23,24,35,40x. Exposure to a stressor has been found to increase CRF mRNA within the central nucleus of the amygdala ŽCeA. w1,16x, an essential site for integrating responses to stressful stimuli w20,27x. The physiological effects of exogenous CRF are similar to that of exposure to a stressor, itself. For example, central administration of CRF increases behavioral activation and arousal while decreasing exploratory behavior in open field and elevated plus maze paradigms w9,15,21,37,39x. Exogenous CRF also increases stress-induced freezing and facilitates acoustic startle and conditioned fear w3,9,14,21x. The behavioral effects of exogenously administered CRF and of stress itself, can be reversed by administration of
0006-8993r99r$ - see front matter q 1999 Elsevier Science B.V. All rights reserved. PII: S 0 0 0 6 - 8 9 9 3 Ž 9 9 . 0 2 0 0 7 - 7
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CRF antagonists w11,25,26,28,30,38x. The effects of exogenously administered CRF continue following hypophysectomy suggesting that CRF may be involved in mediating behavioral responses to stressors independent of the pituitary–adrenal axis w10x. In their natural environment, Syrian hamsters are believed to be solitary animals that defend home territories w31x. When housed singly under laboratory conditions, hamsters attack novel conspecific intruders introduced into their home cage. This aggression most likely represents normal territorial defense. Following brief repeated defeats by a larger, aggressive resident, however, hamsters exhibit submissive and defensive behaviors rather than displaying normal territorial aggression, even when exposed in their own home cage to a smaller, nonaggressive male w33x. This phenomenon has been called conditioned defeat ŽCD. and is a unique response to social defeat. Data indicating that CRF can cause behavioral activation similar to that caused by exposure to a stressor, itself, suggests that CRF systems
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may be involved in mediating the expression of CD in male Syrian hamsters. In order to determine whether CRF was involved in mediating the expression of CD, the present study examined whether two competitive CRF antagonists could reduce the expression of CD. In Experiment 1 CP-154,526, a specific non-peptide CRF1 receptor antagonist, was given peripherally to determine whether the drug would reduce the expression of CD. In Experiment 2 D-Phe CRFŽ12 – 41. , a nonspecific CRF1rCRF2 receptor antagonist, infused directly into the brain, was tested.
2. Materials and methods 2.1. Subjects Animals for all experiments were adult male Syrian hamsters Ž Mesocricetus auratus, Charles River Laborato-
Fig. 1. Duration Žs. of submissiverdefensive Žtop left., aggressive Žtop right., social Žbottom left. and non-social Žbottom right. behavior displayed by defeated hamsters that received an i.p. dose Ž0, 15 and 30 mgrkg. of CP-154,526. Values are reported as means" S.E.M. No significant differences in duration of any behaviors were detected between hamsters that received 15 or 30 mgrkg as compared to 0 mgrkg.
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ries. weighing 120–130 g at the beginning of the experiment. Hamsters were housed individually for two weeks prior to testing in a temperature-controlled Ž208C " 28. colony room on a 14:10 h light:dark ŽL:D. cycle with lights off at 1100 h. Additional hamsters weighing 150–180 g were used as resident aggressors for CD training, and hamsters weighing 100–110 g at the beginning of the experiment were used as nonaggressive intruders ŽNAI. during behavioral testing. All animals were housed in Plexiglas cages Ž20 = 40 = 20 cm. with wire mesh tops and food and water were available ad libitum. The experimental and resident aggressor animals’ cages were not changed for 1 week prior to testing. Resident aggressors were housed individually, whereas NAIs were group housed Žfive animalsrcage.. All procedures and protocols were approved by the Georgia State University Institutional Animal Care and Use Committee.
behaviors were recorded as total duration in s over the 5-min testing period: 1. Non-social: locomotorrexploratory, self-groom, nesting, feeding, sleeping. 2. Social: attend, approach, investigate, sniff, touching nose. 3. SubmissiverDefensive: upright and side defense, tail lift, flee, tooth chatter, full submissive posture. 4. Aggressive: upright and side offense, chase, attack, bite. In the CD model, a statistically significant reduction in the duration of submissiverdefensive behaviors andror the exhibition of territorial aggression signifies a reduction in the expression of CD. Immediately following the final testing session, hamsters were decapitated and trunk blood was collected for plasma ACTH radioimmunoassay ŽRIA.. 2.3. Blood collection and ACTH assay
2.2. Experiment 1 Twenty-one adult male Syrian hamsters were trained for CD. On the day of training, animals were transported from the colony room to the training room for the procedure. CD acquisition consisted of a residentrintruder pairing in which an experimental animal was placed into the cage of a resident aggressor for 5 min. Experimental animals were paired randomly with a resident aggressor four times over a period of 1 day. Training began at 0900 h with 2-h intervals between each session. CD hamsters were matched by weight and assigned randomly to either the experimental or control group. Behavioral testing began 1 day after CD acquisition and was completed during the first 2 h of the dark phase of the daily light:dark cycle. Previous studies using CP-154,526 have indicated that doses ranging from 1 mgrkg to 32 mgrkg can produce anxiolytic effects in both rats and mice, can block plasma ACTH response and can bind to CRF1 receptors in vitro w7,25,26,36x. Therefore, experimental animals received either a 15 or 30 mgrkg intraperitoneal Ži.p.. injection of CP-154,526 Žbutyl-ethyl-w2,5-dimethyl-7-Ž2,4,6-trimethylphenyl.-7H-pyrrolo w2,3-d xpyrimidin-4-ylx-amine ŽCP 154,526. Žcourtesy of Pfizer. in 5% ethanol, 5% Tween-80, 0.9% saline 1 h before behavioral testing, whereas control animals received an injection of vehicle 1 h before behavioral testing. The time between injection of CP-154,526 and behavioral testing was chosen to allow adequate penetration of the drug into the central nervous system and was adapted from Mansbach et al. w26x. Animals were given each dose in a counterbalanced order and were therefore tested three times with three days between each testing session. A residentrintruder model was used consisting of placing a non-aggressive intruder into the home cage of the CD animal for 5 min. All sessions were videotaped and were scored later by an observer blind to condition using a computerized behavioral scoring program. The following
Trunk blood was collected in heparinized beakers transferred to microcentrifuge tubes, centrifuged in a refrigerated centrifuge and plasma was stored at y208C until measured by RIA. ACTH was assayed using an RIA kit supplied by INCSTAR for human ACTH as in Huhman et al. w17x using an antiserum raised in rabbits against human ACTH 1 – 24 . This antiserum has been shown to cross-react with many other species’ ACTH ŽINCSTAR, unpublished data.. Because we do not have a purified sample of hamster ACTH, we cannot state with certainty that it
Fig. 2. Plasma ACTH-LI in defeated hamsters that received an i.p. injection Ž0, 15, 30 mgrkg. of CP-154,526. Values are reported in means"S.E.M. of ACTH-like immunoreactivity ŽACTH-LI.. Animals that received either dose of CP-154,526 had a significant reduction in plasma ACTH-LI response as compared to animals that received a vehicle control Ž p- 0.05. ŽU ..
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cross-reacts quantitatively with this antiserum, however, most of the species differences in ACTH occur in the portion of the molecule beyond that with which the antiserum reacts. The standard used in this assay was human ACTH 1 – 39 . The intraassay coefficient of variation was 3%, and all the samples were run in the same assay. Values are reported as ACTH-like immunoreactivity ŽACTH-LI..
were 0.8 mm anterior and 1.1 mm lateral to bregma and 3.4 mm below dura. Lambda and bregma were leveled before implantation of the guide cannula. Hamsters were allowed 1 week of recovery before being used in behavioral experiments. All hamsters were maintained under the same conditions as in Experiment 1.
2.4. Experiment 2
Hamsters underwent CD acquisition as in Experiment 1. In this experiment, animals were matched by weight and assigned randomly to one of three conditions. Control animals received an intracerebroventricular Ži.c.v.. injection of 3 ml of saline 30 min prior to testing. D-Phe CRFŽ12 – 41. at doses ranging from 1 to 25 mg have been shown to completely reverse the stress effect induced by exposure to a social stressor without exhibiting agonist
2.4.1. Surgical procedures At the beginning of the experiment, 21 adult male, Syrian hamsters ŽCharles River. were anesthetized deeply with sodium pentobarbitol Ž90 mgrkg. and were stereotaxically implanted with a 4-mm, 26-gauge guide cannula aimed at the lateral ventricle ŽLV.. Stereotaxic coordinates
2.5. BehaÕioral manipulations
Fig. 3. Duration Žs. of submissiverdefensive Žtop left., aggressive Žtop right., social Žbottom left. and non-social Žbottom right. behavior displayed by defeated hamsters that received an i.c.v. injection Ž0, 5, or 25 mg. of D-Phe CRF. No significant differences in duration of aggressive, social and non-social behaviors were detected. In contrast, the duration of submissiverdefensive behavior was significantly lower in hamsters that received the 25 mg dose of U D-Phe CRF Ž p - 0.05. Ž ..
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properties w30x. Experimental animals received either a 5or 25-mg injection of D-Phe-CRFŽ12 – 41. ŽwD-Phe12 , Nle 21,38 , C R -MeLeu37 x-CRFŽ12 – 41. ; Bachem. diluted in 3 ml of saline 30 min prior to behavioral testing to allow diffusion of the drug. The delay between injection of the peptide antagonist and behavioral testing was justified based on the finding that D-Phe CRFŽ12-41. has an extended duration of action lasting for at least 90 min w30x. Animals were tested as in Experiment 1, and the behavior was scored by an observer blind to the experimental conditions. At the conclusion of the experiment, hamsters were given a lethal dose of sodium pentobarbitol and were injected with 300 nl of blue ink into the LV. Brains were sliced to examine the LV to verify the site of injections. Only animals with injection sites within the LV were included in the analysis. 2.6. Data analysis Behavioral data Žduration of aggressive, submissiver defensive, social and nonsocial behaviors in s. for Experiment 1 were analyzed using a repeated measures analysis of variance ŽANOVA.. Statistical significance was ascribed at p - 0.05. ACTH-LI levels were compared using a one-way between-subjects ANOVA. Behavioral data for Experiment 2 were analyzed using a one-way betweensubjects ANOVA and significant differences were analyzed further using a Tukey post hoc test to compare group differences.
3. Results In Experiment 1, there was no significant reduction of submissiverdefensive behavior in CD animals that received either the 15 Žlow. or 30 mgrkg Žhigh. dose of CP-154,526 as compared to animals that received a vehicle control Ž p ) 0.05., nor was there a significant increase in the display of territorial aggression in those animals that received either dose of CP-154,526 as compared to those that received a vehicle control Ž p ) 0.05. ŽFig. 1.. There were also no significant differences in duration of social and nonsocial behaviors at both the low and high doses as compared to controls Ž p ) 0.05, Fig. 1.. There was, however, a significant reduction in plasma ACTH-LI in animals receiving both the 15 and 30 mgrkg doses of CP164,526 as compared to controls Ž p - 0.05, Fig. 2.. In Experiment 2, there was a significant reduction in the duration of submissiverdefensive behaviors in the group receiving D-Phe CRFŽ12 – 41. as compared to those receiving a vehicle control Žp - 0.05.. Animals that received the 25 mg Žhigh. dose of D-Phe CRFŽ12 – 41. displayed significantly less submissiverdefensive behaviors as compared to the animals that received a vehicle control ŽFig. 3.. There also was a non-significant trend towards an increase in the duration of aggressive behavior in animals that received
the high dose of D-Phe CRFŽ12 – 41. as compared to animals that received the low dose and the vehicle control. No significant differences were detected in the duration of non-social and social behaviors between animals receiving either dose of D-Phe CRFŽ12 – 41. and those receiving a vehicle control ŽFig. 3..
4. Discussion The present data indicate that i.p. administration of the non-peptide, selective CRF1 receptor antagonist, CP154,526, failed to reduce the expression of CD. Administration of CP-154,526, however, successfully reduced stress-induced ACTH release. Plasma ACTH levels in defeated hamsters that received CP-154,526 were similar to those previously measured in undefeated control animals, approximately 60–70 pgrml w19x, whereas defeated hamsters that received a vehicle control exhibited significantly higher plasma ACTH levels. A number of studies in which CRF antagonists have been administered reported a similar reduction in ACTH levels both when animals have been given exogenous CRF and when they have been exposed other stressors w8,36,41x. These data indicate that CP-154,526 blocks CRF1 receptors effectively in the pituitary. In addition, the present data are consistent with previous findings which suggest that behavioral responses to social stressors may be independent of CRF-induced ACTH and glucocorticoid release w32x. In Experiment 2, i.c.v. injections of the non-selective, peptide CRF1rCRF2 receptor antagonist successfully reduced the expression of CD. Animals that received D-Phe CRFŽ12 – 41. Ž25 mg. displayed significantly less submissiverdefensive behaviors in response to a smaller, NAI than did animals that received a vehicle control. This behavioral effect did not appear to be due to a general sedation because no differences were observed in duration of social or nonsocial behaviors. A slight increase in the duration of aggressive behavior was observed in animals that received the high dose of D-Phe CRFŽ12 – 41. and, although this effect did not reach statistical significance, it remains interesting because hamsters that have undergone CD training generally fail to display any territorial aggression. These data, together with previous data indicating that CRF antagonists produce anxiolytic-like effects in other social stress models and in tests of anxiety w11,13,15,22,25,26,28,30,38 x, suggest that central CRF systems may mediate the expression of CD in Syrian hamsters. The finding that CP-154,526 failed to reduce the expression of CD contradicts previous studies reporting anxiolytic-like effects of CP-154,526 w25,26,36x. One possible explanation for the discrepancy is that the doses were too low in the present study; however, this possibility seems unlikely because both the 15 and 30 mgrkg dose blocked plasma ACTH response to near baseline levels. This indi-
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cates that the doses were adequate to block CRF1 receptors successfully outside the brain. Another explanation for these results is that CP-154,526 may not effectively cross the blood brain barrier in hamsters, although ex vivo binding and autoradiographic studies have shown excellent receptor occupation after peripheral administration of CP154,526 in rats ŽDr. David Schulz, personal communication.. Recently, the anxiolytic effects of CP-154,526 were reassessed in both rats and mice with a battery of tests including punished lever pressing and drinking, the elevated plus maze, lightrdark choice, free-exploration tests and the mouse defense test battery. CP-154,526 was devoid of any significant anxiolytic-like effects on nearly all the tests of anxiety w12x. Together, these data question the general effectiveness of CP-154,526 in reducing the anxiogenic effects of stressors including, perhaps, social defeat. The specific role that both CRF1 and CRF2 receptors play in mediating behavioral and emotional response to stressors remains unclear. Because CP-154,526 failed to reduce the expression of CD, the present findings may indicate that CRF1 receptors are not involved in mediating CD in hamsters. We cannot determine if this is the case, however, because a binding assay of CP-154,526 to hamster brain CRF1 receptors was not performed. Moreover, because D-Phe CRFŽ12 – 41. is a non-selective CRF1rCRF2 receptor antagonist, the attenuation of CD in Experiment 2 could be due to binding at either CRF receptor or at a combination of both receptors. The current data, together with previous studies showing anxiolytic effects of CRF antagonists, do suggest, however, that central CRF is involved in mediating the expression of conditioned defeat and behavioral responses to social stress, in general.
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We would to thank Pfizer for their donation of CP154,526, and Dr. James Meyerhoff for the ACTH radioimmunoassay. Supported by NS34896 to KLH.
References w1x D.S. Albeck, C.R. Mckittrick, D.C. Blanchard, R.J. Blanchard, J. Nikulina, B.S. McEwen, R.R. Sakai, Chronic social stress alters levels of corticotropin-releasing factor and arginine vasopressin mRNA in rat brain, J. Neurosci. 17 Ž1997. 4895–4903. w2x M.E. Albonetti, F. Farabollini, Social stress by repeated defeats: effects on social behaviour and emotionality, Behav. Brain Res. 62 Ž1994. 187–193. w3x H.A. Baldwin, K.T. Britton, G.F. Koob, Behavioral effects of corticotropin-releasing factor, in: D. Pfaff, D. Ganten ŽEds.., Behavioral Aspects of Neuroendocrinology, Current Topics in Neuroendocrinology, Springer-Verlag, Berlin, 1990. w4x D.C. Blanchard, R.L. Spencer, S.M. Weiss, R.J. Blanchard, B.S. McEwen, R.R. Sakai, Visible burrow system as a model of chronic
w17x
w18x
w19x
w20x
w21x
127
social stress: behavioral and neuroendocrine correlates, Psychoneuroendocrinology 20 Ž1995. 117–134. B. Bohus, J.M. Koolhaas, C.J. Heijnen, O. de Boer, Immunological responses to social stress: dependence on social environment and coping abilities, Neuropsychobiology 28 Ž1993. 95–99. D.T. Chalmers, T.W. Lovenberg, E.B. De Souza, Localization of novel corticotropin-releasing factor receptor ŽCRF2 . mRNA expression to specific subcortical nuclei in rat brain: comparison with CRF1 receptor mRNA expression, J. Neurosci. 15 Ž1995. 6340–6350. Y.L. Chen, R.S. Mansbach, S.M. Winter, E. Brooks, J. Collins, M.L. Corman, A. Dunaiskis, S. Faraci, R.J. Gallaschun, A.W. Schmidt, D.W. Schulz, Synthesis and oral efficacy of a 4-Žbutylethylamino.pyrrolow2,3-d xpyrimidine: a centrally active corticotropin-releasing factor1 receptor antagonist, J. Med. Chem. 40 Ž1997. 1749–1754. T. Deak, K.T. Nguyen, A.L. Ehrlich, L.R. Watkins, R.L. Spencer, S.F. Maier, J. Licinio, M.L. Wong, G.P. Chrousos, E. Webster, P.W. Gold, The impact of the nonpeptide corticotropin-releasing hormone antagonist Antalarmin on behavioral and endocrine responses to stress, Endocrinology 140 Ž1999. 76–86. A.J. Dunn, C.W. Berridge, Physiological and behavioral responses to corticotropin-releasing factor administration: is CRF a mediator of anxiety or stress responses?, Brain Res. Rev. 15 Ž1990. 71–100. M. Eaves, K.T. Britton, J. Rivier, W. Vale, G.F. Koob, Effects of corticotropin-releasing factor on locomotor activity in hypophysectomized rats, Peptides 6 Ž1985. 923–926. M. Fendt, M. Koch, H.-U. Schnitzler, Corticotropin-releasing factor in the caudal pontine reticular nucleus mediates the expression of fear-potentiated startle in the rat, Eur. J. Neurosci. 9 Ž1997. 299–305. G. Griebel, G. Perrault, D.J. Sanger, Characterization of the behavioral profile of the non-peptide CRF receptor antagonist CP-154,526 in anxiety models in rodents: comparison with diazepam and buspirone, Psychopharmacology 138 Ž1998. 55–66. S.C. Heinrichs, J. Lapansky, T.W. Lovenberg, E.B. De Souza, D.T. Chalmers, Corticotropin-releasing factor CRF1 , but not CRF2 , receptors mediate anxiogenic-like behavior, Regul. Pept. 23 Ž1997. 15–21. S.C. Heinrichs, F. Menzaghi, E.M. Pich, K.T. Britton, G.F. Koob, The role of CRF in behavioral aspects of stress, Ann. N. Y. Acad. Sci. 771 Ž1995. 92–104. S.C. Heinrichs, E.M. Pich, K.A. Miczek, K.T. Britton, G.F. Koob, Corticotropin-releasing factor antagonist reduces emotionality in socially defeated rats via direct neurotropic action, Brain Res. 581 Ž1992. 190–197. D.T. Hsu, F.-L. Chen, L.K. Takahashi, N.H. Kalin, Rapid stress-induced elevations in corticotropin-releasing hormone mRNA in rat central amygdala nucleus and hypothalamic paraventricular nucleus: an in situ hybridization analysis, Brain Res. 788 Ž1998. 305–310. K.L. Huhman, B.N. Bunnell, E.H. Mougey, J.L. Meyerhoff, Effects of social conflict on POMC-derived peptides and glucocorticoids in male golden hamsters, Physiol. Behav. 47 Ž1990. 949–956. K.L. Huhman, T.O. Moore, C.F. Ferris, E.H. Mougey, J.L. Meyerhoff, Acute and repeated exposure to social conflict in male golden hamsters: increases in plasma POMC-peptides and cortisol and decreases in plasma testosterone, Horm. Behav. 25 Ž1991. 206–216. K.L. Huhman, T.O. Moore, E.H. Mougey, J.L. Meyerhoff, Hormonal responses to fighting in hamsters: separation of physical and psychological causes, Physiol. Behav. 51 Ž1992. 1083–1086. S. Kollack-Walker, S.J. Watson, H. Akil, Social stress in hamsters: defeat activates specific neurocircuits within the brain, J. Neurosci. 17 Ž1997. 8842–8855. G.F. Koob, S.C. Heinrichs, E. Merlo-Pich, F. Menzaghi, H.A. Baldwin, K.A. Miczek, K.T. Britton, The role of corticotropin-releasing factor in behavioral responses to stress, in: E.B. De Souza, C.B. Nemeroff ŽEds.., Corticotropin-releasing factor: Basic and clinical studies of a neuropeptide, CRC Press, Boca Raton, 1993, pp. 277–295.
128
A.M. Jasnow et al.r Brain Research 846 (1999) 122–128
w22x S.M. Korte, A.H. Korte-Bouws, B. Bohus, G.F. Koob, Effect of corticotropin-releasing factor antagonist on behavioral and neuroendocrine responses during exposure to defensive burying paradigm in rats, Physiol. Behav. 56 Ž1994. 115–120. w23x H. Lehnert, C. Schulz, K. Dieterich, Physiological and neurochemical aspects of corticotropin-releasing factor actions in the brain: the role of the locus coeruleus, Neurochem. Res. 23 Ž1998. 1039–1052. w24x T.W. Lovenberg, D.T. Chalmers, E.B. De Souza, CRF2 a and CRF2b receptor mRNA’s are differentially distributed between the rat central nervous system and peripheral tissues, Endocrinology 136 Ž1995. 4139–4142. w25x J. Lundkvist, Z. Chai, R. Teheranian, H. Hasanvan, T. Bartfai, F. Jenck, U. Widmer, J.-L. Moreau, A non peptidic corticotropin releasing factor receptor antagonist attenuates fever and exhibits anxiolytic-like activity, Eur. J. Pharmacol. 309 Ž1996. 195–200. w26x R.S. Mansbach, E.N. Brooks, Y.L. Chen, Antidepressant-like effects of CP-154,526, a selective CRF1 receptor antagonist, Eur. J. Pharmacol. 323 Ž1997. 21–26. w27x S. Maren, M.S. Fanselow, The amygdala and fear conditioning: has the nut been cracked?, Neuron 16 Ž1996. 237–240. w28x A.P. Martins, R.A. Marras, F.S. Guimaraes, Anxiogenic effect of corticotropin-releasing hormone in the dorsal periaqueductal grey, NeuroReport 8 Ž1997. 3601–3604. w29x W.P. Meehan, W. Tornatzky, K.A. Miczek, Blood pressure via telemetry during social confrontations in rats: effects of clonidine, Physiol. Behav. 58 Ž1995. 81–88. w30x F. Menzaghi, R.L. Howard, S.C. Heinrichs, W. Vale, J. Rivier, G.F. Koob, Characterization of a novel and potent corticotropin-releasing factor antagonist in rats, J. Pharmacol. Exp. Ther. 269 Ž1994. 564–572. w31x R.M. Nowack, J.L. Paradiso, Walker’s Mammals of the World, Johns Hopkins Univ. Press, Baltimore, MD, 1983. w32x E.M. Pich, S.C. Heinrichs, C. Rivier, K.A. Miczek, D.A. Fisher, G.F. Koob, Blockade of pituitary–adrenal axis activation induced by
w33x w34x
w35x
w36x
w37x w38x
w39x
w40x
w41x
peripheral immunoneutralization of corticotropin-releasing factor does not affect the behavioral response to social defeat stress in rats, Psychoneuroendocrinology 18 Ž1993. 495–507. M. Potegal, K.L. Huhman, J.L. Meyerhoff, Conditioned defeat in the Syrian hamster, Behav. Neural Biol. 60 Ž1993. 93–102. R.J. Rodgers, J.C. Cole, Anxiety enhancement in the murine elevated plus maze by immediate prior exposure to social stressors, Physiol. Behav. 53 Ž1993. 383–388. E. Sawchenko, L.W. Swanson, Localization, colocalization, and plasticity of corticotropin-releasing factor immunoreactivity in the brain, Fed. Proc. 44 Ž1985. 221–227. D.W. Schulz, R.S. Mansbach, J. Sprouse, J.P. Braselton, J. Collins, M. Corman, A. Dunaiskis, S. Faraci, A.W. Schmidt, T. Seeger, P. Seymour, F.D. Tingley III, E.N. Winston, Y.L. Chen, J. Heym, CP-154,526: A potent and selective nonpeptide antagonist of corticotropin-releasing factor receptors, Pharmacology 93 Ž1996. 10477– 10482. J.E. Sherman, N.H. Kalin, The effects of i.c.v.-CRH on novelty-induced behavior, Pharmacol. Biochem. Behav. 26 Ž1987. 699–703. G.N. Smagin, R.B. Harris, D.H. Ryan, Corticotropin-releasing factor receptor antagonist infused into the locus coeruleus attenuates immobilization stress-induced defensive withdrawal in rats, Neurosci. Lett. 220 Ž1996. 167–170. R. Sutton, G.F. Koob, M. Le Moal, J. Rivier, W. Vale, Corticotropin-releasing factor ŽCRF. produces behavioral activation in rats, Nature 299 Ž1982. 331–333. R.J. Valentino, S.L. Foote, M.E. Page, The locus coeruleus as a site for integrating corticotropin-releasing factor and noradrenergic mediation of stress responses, Ann. N. Y. Acad. Sci. 697 Ž1993. 173–188. E.L. Webster, D.B. Lewis, D.J. Torpy, E.K. Zachman, K.C. Rice, G.P. Chrousos, In vivo and in vitro characterization of Antalarmin, a nonpeptide corticotropin-releasing hormone ŽCRH. receptor antagonist: suppression of pituitary ACTH release and peripheral inflammation, Endocrinology 137 Ž1996. 5747–5750.
Research report
Differential effects of two corticotropin-releasing factor antagonists on conditioned defeat in male Syrian hamsters ŽMesocricetus auratus . Aaron M. Jasnow, Matia C. Banks, Elizabeth C. Owens, Kim L. Huhman
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Laboratory of BehaÕioral Neuroscience, Department of Psychology, Georgia State UniÕersity, Atlanta, GA 30303, USA Accepted 17 August 1999
Abstract The purpose of the present study was to determine whether corticotropin-releasing factor ŽCRF. is involved in mediating the expression of conditioned defeat in male Syrian hamsters. The present study examined the effects of two different competitive CRF receptor antagonists on the expression of conditioned defeat. Specifically, Experiment 1 examined whether peripheral administration of CP-154,526, a specific non-peptide CRF1 receptor antagonist, would reduce the expression of conditioned defeat. Experiment 2 examined whether D-Phe CRFŽ12 – 41. , a nonspecific CRF1rCRF2 receptor antagonist, infused directly into the brain, would reduce the expression of conditioned defeat. The results revealed that i.p. injections of CP-154,526 did not reduce the expression of conditioned defeat, whereas i.c.v. injections of D-Phe CRFŽ12 – 41. successfully reduced the expression of conditioned defeat. The duration of submissiverdefensive behaviors in hamsters that received the high dose of D-Phe CRFŽ12 – 41. was significantly less than that exhibited by animals that received a vehicle control. The present data suggest that central CRF may be involved in mediating the expression of conditioned defeat and other behavioral responses to stressful stimuli. q 1999 Elsevier Science B.V. All rights reserved. Keywords: Corticotropin-releasing factor; Social stress; Aggression; Agonistic behavior
1. Introduction Many animal species are exposed to social stressors during their lifetime. These stressors may include territorial conflict, competition for food and competition between males for access to females. In these conflicts there is usually a winner and a loser. Defeated animals display an increased activation of the hypothalamic–pituitary–adrenal ŽHPA. axis as evidenced by increased release of adrenocorticotropin ŽACTH., b-endorphin, cortisol and corticosterone. Dominant animals, however, display no such hormonal stress response w17–19x. Several lines of evidence suggest that social defeat also results in lasting autonomic and behavioral changes. Following a brief agonistic encounter, defeated animals exhibit increased blood pressure and heart rate and have compromised immune function w4,5,29x. The behavioral changes that may occur following defeat include decreased reproductive behavior, decreased food and water intake, decreased exploratory behavior, increased anxiety and decreased aggressive behavior ) Corresponding [email protected]
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w2,15,33,34x. These data suggest that losing a fight results in a suite of physiological, behavioral and autonomic changes, some of which may become deleterious to the defeated animal. Corticotropin-releasing factor ŽCRF. traditionally has been considered the primary neurohormone mediating the activity of the HPA axis; however, the localization of CRF-containing cell bodies and CRF receptors in extrahypothalamic brain areas suggests that CRF also may be involved in mediating autonomic and behavioral responses to stressors w6,23,24,35,40x. Exposure to a stressor has been found to increase CRF mRNA within the central nucleus of the amygdala ŽCeA. w1,16x, an essential site for integrating responses to stressful stimuli w20,27x. The physiological effects of exogenous CRF are similar to that of exposure to a stressor, itself. For example, central administration of CRF increases behavioral activation and arousal while decreasing exploratory behavior in open field and elevated plus maze paradigms w9,15,21,37,39x. Exogenous CRF also increases stress-induced freezing and facilitates acoustic startle and conditioned fear w3,9,14,21x. The behavioral effects of exogenously administered CRF and of stress itself, can be reversed by administration of
0006-8993r99r$ - see front matter q 1999 Elsevier Science B.V. All rights reserved. PII: S 0 0 0 6 - 8 9 9 3 Ž 9 9 . 0 2 0 0 7 - 7
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CRF antagonists w11,25,26,28,30,38x. The effects of exogenously administered CRF continue following hypophysectomy suggesting that CRF may be involved in mediating behavioral responses to stressors independent of the pituitary–adrenal axis w10x. In their natural environment, Syrian hamsters are believed to be solitary animals that defend home territories w31x. When housed singly under laboratory conditions, hamsters attack novel conspecific intruders introduced into their home cage. This aggression most likely represents normal territorial defense. Following brief repeated defeats by a larger, aggressive resident, however, hamsters exhibit submissive and defensive behaviors rather than displaying normal territorial aggression, even when exposed in their own home cage to a smaller, nonaggressive male w33x. This phenomenon has been called conditioned defeat ŽCD. and is a unique response to social defeat. Data indicating that CRF can cause behavioral activation similar to that caused by exposure to a stressor, itself, suggests that CRF systems
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may be involved in mediating the expression of CD in male Syrian hamsters. In order to determine whether CRF was involved in mediating the expression of CD, the present study examined whether two competitive CRF antagonists could reduce the expression of CD. In Experiment 1 CP-154,526, a specific non-peptide CRF1 receptor antagonist, was given peripherally to determine whether the drug would reduce the expression of CD. In Experiment 2 D-Phe CRFŽ12 – 41. , a nonspecific CRF1rCRF2 receptor antagonist, infused directly into the brain, was tested.
2. Materials and methods 2.1. Subjects Animals for all experiments were adult male Syrian hamsters Ž Mesocricetus auratus, Charles River Laborato-
Fig. 1. Duration Žs. of submissiverdefensive Žtop left., aggressive Žtop right., social Žbottom left. and non-social Žbottom right. behavior displayed by defeated hamsters that received an i.p. dose Ž0, 15 and 30 mgrkg. of CP-154,526. Values are reported as means" S.E.M. No significant differences in duration of any behaviors were detected between hamsters that received 15 or 30 mgrkg as compared to 0 mgrkg.
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ries. weighing 120–130 g at the beginning of the experiment. Hamsters were housed individually for two weeks prior to testing in a temperature-controlled Ž208C " 28. colony room on a 14:10 h light:dark ŽL:D. cycle with lights off at 1100 h. Additional hamsters weighing 150–180 g were used as resident aggressors for CD training, and hamsters weighing 100–110 g at the beginning of the experiment were used as nonaggressive intruders ŽNAI. during behavioral testing. All animals were housed in Plexiglas cages Ž20 = 40 = 20 cm. with wire mesh tops and food and water were available ad libitum. The experimental and resident aggressor animals’ cages were not changed for 1 week prior to testing. Resident aggressors were housed individually, whereas NAIs were group housed Žfive animalsrcage.. All procedures and protocols were approved by the Georgia State University Institutional Animal Care and Use Committee.
behaviors were recorded as total duration in s over the 5-min testing period: 1. Non-social: locomotorrexploratory, self-groom, nesting, feeding, sleeping. 2. Social: attend, approach, investigate, sniff, touching nose. 3. SubmissiverDefensive: upright and side defense, tail lift, flee, tooth chatter, full submissive posture. 4. Aggressive: upright and side offense, chase, attack, bite. In the CD model, a statistically significant reduction in the duration of submissiverdefensive behaviors andror the exhibition of territorial aggression signifies a reduction in the expression of CD. Immediately following the final testing session, hamsters were decapitated and trunk blood was collected for plasma ACTH radioimmunoassay ŽRIA.. 2.3. Blood collection and ACTH assay
2.2. Experiment 1 Twenty-one adult male Syrian hamsters were trained for CD. On the day of training, animals were transported from the colony room to the training room for the procedure. CD acquisition consisted of a residentrintruder pairing in which an experimental animal was placed into the cage of a resident aggressor for 5 min. Experimental animals were paired randomly with a resident aggressor four times over a period of 1 day. Training began at 0900 h with 2-h intervals between each session. CD hamsters were matched by weight and assigned randomly to either the experimental or control group. Behavioral testing began 1 day after CD acquisition and was completed during the first 2 h of the dark phase of the daily light:dark cycle. Previous studies using CP-154,526 have indicated that doses ranging from 1 mgrkg to 32 mgrkg can produce anxiolytic effects in both rats and mice, can block plasma ACTH response and can bind to CRF1 receptors in vitro w7,25,26,36x. Therefore, experimental animals received either a 15 or 30 mgrkg intraperitoneal Ži.p.. injection of CP-154,526 Žbutyl-ethyl-w2,5-dimethyl-7-Ž2,4,6-trimethylphenyl.-7H-pyrrolo w2,3-d xpyrimidin-4-ylx-amine ŽCP 154,526. Žcourtesy of Pfizer. in 5% ethanol, 5% Tween-80, 0.9% saline 1 h before behavioral testing, whereas control animals received an injection of vehicle 1 h before behavioral testing. The time between injection of CP-154,526 and behavioral testing was chosen to allow adequate penetration of the drug into the central nervous system and was adapted from Mansbach et al. w26x. Animals were given each dose in a counterbalanced order and were therefore tested three times with three days between each testing session. A residentrintruder model was used consisting of placing a non-aggressive intruder into the home cage of the CD animal for 5 min. All sessions were videotaped and were scored later by an observer blind to condition using a computerized behavioral scoring program. The following
Trunk blood was collected in heparinized beakers transferred to microcentrifuge tubes, centrifuged in a refrigerated centrifuge and plasma was stored at y208C until measured by RIA. ACTH was assayed using an RIA kit supplied by INCSTAR for human ACTH as in Huhman et al. w17x using an antiserum raised in rabbits against human ACTH 1 – 24 . This antiserum has been shown to cross-react with many other species’ ACTH ŽINCSTAR, unpublished data.. Because we do not have a purified sample of hamster ACTH, we cannot state with certainty that it
Fig. 2. Plasma ACTH-LI in defeated hamsters that received an i.p. injection Ž0, 15, 30 mgrkg. of CP-154,526. Values are reported in means"S.E.M. of ACTH-like immunoreactivity ŽACTH-LI.. Animals that received either dose of CP-154,526 had a significant reduction in plasma ACTH-LI response as compared to animals that received a vehicle control Ž p- 0.05. ŽU ..
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cross-reacts quantitatively with this antiserum, however, most of the species differences in ACTH occur in the portion of the molecule beyond that with which the antiserum reacts. The standard used in this assay was human ACTH 1 – 39 . The intraassay coefficient of variation was 3%, and all the samples were run in the same assay. Values are reported as ACTH-like immunoreactivity ŽACTH-LI..
were 0.8 mm anterior and 1.1 mm lateral to bregma and 3.4 mm below dura. Lambda and bregma were leveled before implantation of the guide cannula. Hamsters were allowed 1 week of recovery before being used in behavioral experiments. All hamsters were maintained under the same conditions as in Experiment 1.
2.4. Experiment 2
Hamsters underwent CD acquisition as in Experiment 1. In this experiment, animals were matched by weight and assigned randomly to one of three conditions. Control animals received an intracerebroventricular Ži.c.v.. injection of 3 ml of saline 30 min prior to testing. D-Phe CRFŽ12 – 41. at doses ranging from 1 to 25 mg have been shown to completely reverse the stress effect induced by exposure to a social stressor without exhibiting agonist
2.4.1. Surgical procedures At the beginning of the experiment, 21 adult male, Syrian hamsters ŽCharles River. were anesthetized deeply with sodium pentobarbitol Ž90 mgrkg. and were stereotaxically implanted with a 4-mm, 26-gauge guide cannula aimed at the lateral ventricle ŽLV.. Stereotaxic coordinates
2.5. BehaÕioral manipulations
Fig. 3. Duration Žs. of submissiverdefensive Žtop left., aggressive Žtop right., social Žbottom left. and non-social Žbottom right. behavior displayed by defeated hamsters that received an i.c.v. injection Ž0, 5, or 25 mg. of D-Phe CRF. No significant differences in duration of aggressive, social and non-social behaviors were detected. In contrast, the duration of submissiverdefensive behavior was significantly lower in hamsters that received the 25 mg dose of U D-Phe CRF Ž p - 0.05. Ž ..
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properties w30x. Experimental animals received either a 5or 25-mg injection of D-Phe-CRFŽ12 – 41. ŽwD-Phe12 , Nle 21,38 , C R -MeLeu37 x-CRFŽ12 – 41. ; Bachem. diluted in 3 ml of saline 30 min prior to behavioral testing to allow diffusion of the drug. The delay between injection of the peptide antagonist and behavioral testing was justified based on the finding that D-Phe CRFŽ12-41. has an extended duration of action lasting for at least 90 min w30x. Animals were tested as in Experiment 1, and the behavior was scored by an observer blind to the experimental conditions. At the conclusion of the experiment, hamsters were given a lethal dose of sodium pentobarbitol and were injected with 300 nl of blue ink into the LV. Brains were sliced to examine the LV to verify the site of injections. Only animals with injection sites within the LV were included in the analysis. 2.6. Data analysis Behavioral data Žduration of aggressive, submissiver defensive, social and nonsocial behaviors in s. for Experiment 1 were analyzed using a repeated measures analysis of variance ŽANOVA.. Statistical significance was ascribed at p - 0.05. ACTH-LI levels were compared using a one-way between-subjects ANOVA. Behavioral data for Experiment 2 were analyzed using a one-way betweensubjects ANOVA and significant differences were analyzed further using a Tukey post hoc test to compare group differences.
3. Results In Experiment 1, there was no significant reduction of submissiverdefensive behavior in CD animals that received either the 15 Žlow. or 30 mgrkg Žhigh. dose of CP-154,526 as compared to animals that received a vehicle control Ž p ) 0.05., nor was there a significant increase in the display of territorial aggression in those animals that received either dose of CP-154,526 as compared to those that received a vehicle control Ž p ) 0.05. ŽFig. 1.. There were also no significant differences in duration of social and nonsocial behaviors at both the low and high doses as compared to controls Ž p ) 0.05, Fig. 1.. There was, however, a significant reduction in plasma ACTH-LI in animals receiving both the 15 and 30 mgrkg doses of CP164,526 as compared to controls Ž p - 0.05, Fig. 2.. In Experiment 2, there was a significant reduction in the duration of submissiverdefensive behaviors in the group receiving D-Phe CRFŽ12 – 41. as compared to those receiving a vehicle control Žp - 0.05.. Animals that received the 25 mg Žhigh. dose of D-Phe CRFŽ12 – 41. displayed significantly less submissiverdefensive behaviors as compared to the animals that received a vehicle control ŽFig. 3.. There also was a non-significant trend towards an increase in the duration of aggressive behavior in animals that received
the high dose of D-Phe CRFŽ12 – 41. as compared to animals that received the low dose and the vehicle control. No significant differences were detected in the duration of non-social and social behaviors between animals receiving either dose of D-Phe CRFŽ12 – 41. and those receiving a vehicle control ŽFig. 3..
4. Discussion The present data indicate that i.p. administration of the non-peptide, selective CRF1 receptor antagonist, CP154,526, failed to reduce the expression of CD. Administration of CP-154,526, however, successfully reduced stress-induced ACTH release. Plasma ACTH levels in defeated hamsters that received CP-154,526 were similar to those previously measured in undefeated control animals, approximately 60–70 pgrml w19x, whereas defeated hamsters that received a vehicle control exhibited significantly higher plasma ACTH levels. A number of studies in which CRF antagonists have been administered reported a similar reduction in ACTH levels both when animals have been given exogenous CRF and when they have been exposed other stressors w8,36,41x. These data indicate that CP-154,526 blocks CRF1 receptors effectively in the pituitary. In addition, the present data are consistent with previous findings which suggest that behavioral responses to social stressors may be independent of CRF-induced ACTH and glucocorticoid release w32x. In Experiment 2, i.c.v. injections of the non-selective, peptide CRF1rCRF2 receptor antagonist successfully reduced the expression of CD. Animals that received D-Phe CRFŽ12 – 41. Ž25 mg. displayed significantly less submissiverdefensive behaviors in response to a smaller, NAI than did animals that received a vehicle control. This behavioral effect did not appear to be due to a general sedation because no differences were observed in duration of social or nonsocial behaviors. A slight increase in the duration of aggressive behavior was observed in animals that received the high dose of D-Phe CRFŽ12 – 41. and, although this effect did not reach statistical significance, it remains interesting because hamsters that have undergone CD training generally fail to display any territorial aggression. These data, together with previous data indicating that CRF antagonists produce anxiolytic-like effects in other social stress models and in tests of anxiety w11,13,15,22,25,26,28,30,38 x, suggest that central CRF systems may mediate the expression of CD in Syrian hamsters. The finding that CP-154,526 failed to reduce the expression of CD contradicts previous studies reporting anxiolytic-like effects of CP-154,526 w25,26,36x. One possible explanation for the discrepancy is that the doses were too low in the present study; however, this possibility seems unlikely because both the 15 and 30 mgrkg dose blocked plasma ACTH response to near baseline levels. This indi-
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cates that the doses were adequate to block CRF1 receptors successfully outside the brain. Another explanation for these results is that CP-154,526 may not effectively cross the blood brain barrier in hamsters, although ex vivo binding and autoradiographic studies have shown excellent receptor occupation after peripheral administration of CP154,526 in rats ŽDr. David Schulz, personal communication.. Recently, the anxiolytic effects of CP-154,526 were reassessed in both rats and mice with a battery of tests including punished lever pressing and drinking, the elevated plus maze, lightrdark choice, free-exploration tests and the mouse defense test battery. CP-154,526 was devoid of any significant anxiolytic-like effects on nearly all the tests of anxiety w12x. Together, these data question the general effectiveness of CP-154,526 in reducing the anxiogenic effects of stressors including, perhaps, social defeat. The specific role that both CRF1 and CRF2 receptors play in mediating behavioral and emotional response to stressors remains unclear. Because CP-154,526 failed to reduce the expression of CD, the present findings may indicate that CRF1 receptors are not involved in mediating CD in hamsters. We cannot determine if this is the case, however, because a binding assay of CP-154,526 to hamster brain CRF1 receptors was not performed. Moreover, because D-Phe CRFŽ12 – 41. is a non-selective CRF1rCRF2 receptor antagonist, the attenuation of CD in Experiment 2 could be due to binding at either CRF receptor or at a combination of both receptors. The current data, together with previous studies showing anxiolytic effects of CRF antagonists, do suggest, however, that central CRF is involved in mediating the expression of conditioned defeat and behavioral responses to social stress, in general.
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We would to thank Pfizer for their donation of CP154,526, and Dr. James Meyerhoff for the ACTH radioimmunoassay. Supported by NS34896 to KLH.
References w1x D.S. Albeck, C.R. Mckittrick, D.C. Blanchard, R.J. Blanchard, J. Nikulina, B.S. McEwen, R.R. Sakai, Chronic social stress alters levels of corticotropin-releasing factor and arginine vasopressin mRNA in rat brain, J. Neurosci. 17 Ž1997. 4895–4903. w2x M.E. Albonetti, F. Farabollini, Social stress by repeated defeats: effects on social behaviour and emotionality, Behav. Brain Res. 62 Ž1994. 187–193. w3x H.A. Baldwin, K.T. Britton, G.F. Koob, Behavioral effects of corticotropin-releasing factor, in: D. Pfaff, D. Ganten ŽEds.., Behavioral Aspects of Neuroendocrinology, Current Topics in Neuroendocrinology, Springer-Verlag, Berlin, 1990. w4x D.C. Blanchard, R.L. Spencer, S.M. Weiss, R.J. Blanchard, B.S. McEwen, R.R. Sakai, Visible burrow system as a model of chronic
w17x
w18x
w19x
w20x
w21x
127
social stress: behavioral and neuroendocrine correlates, Psychoneuroendocrinology 20 Ž1995. 117–134. B. Bohus, J.M. Koolhaas, C.J. Heijnen, O. de Boer, Immunological responses to social stress: dependence on social environment and coping abilities, Neuropsychobiology 28 Ž1993. 95–99. D.T. Chalmers, T.W. Lovenberg, E.B. De Souza, Localization of novel corticotropin-releasing factor receptor ŽCRF2 . mRNA expression to specific subcortical nuclei in rat brain: comparison with CRF1 receptor mRNA expression, J. Neurosci. 15 Ž1995. 6340–6350. Y.L. Chen, R.S. Mansbach, S.M. Winter, E. Brooks, J. Collins, M.L. Corman, A. Dunaiskis, S. Faraci, R.J. Gallaschun, A.W. Schmidt, D.W. Schulz, Synthesis and oral efficacy of a 4-Žbutylethylamino.pyrrolow2,3-d xpyrimidine: a centrally active corticotropin-releasing factor1 receptor antagonist, J. Med. Chem. 40 Ž1997. 1749–1754. T. Deak, K.T. Nguyen, A.L. Ehrlich, L.R. Watkins, R.L. Spencer, S.F. Maier, J. Licinio, M.L. Wong, G.P. Chrousos, E. Webster, P.W. Gold, The impact of the nonpeptide corticotropin-releasing hormone antagonist Antalarmin on behavioral and endocrine responses to stress, Endocrinology 140 Ž1999. 76–86. A.J. Dunn, C.W. Berridge, Physiological and behavioral responses to corticotropin-releasing factor administration: is CRF a mediator of anxiety or stress responses?, Brain Res. Rev. 15 Ž1990. 71–100. M. Eaves, K.T. Britton, J. Rivier, W. Vale, G.F. Koob, Effects of corticotropin-releasing factor on locomotor activity in hypophysectomized rats, Peptides 6 Ž1985. 923–926. M. Fendt, M. Koch, H.-U. Schnitzler, Corticotropin-releasing factor in the caudal pontine reticular nucleus mediates the expression of fear-potentiated startle in the rat, Eur. J. Neurosci. 9 Ž1997. 299–305. G. Griebel, G. Perrault, D.J. Sanger, Characterization of the behavioral profile of the non-peptide CRF receptor antagonist CP-154,526 in anxiety models in rodents: comparison with diazepam and buspirone, Psychopharmacology 138 Ž1998. 55–66. S.C. Heinrichs, J. Lapansky, T.W. Lovenberg, E.B. De Souza, D.T. Chalmers, Corticotropin-releasing factor CRF1 , but not CRF2 , receptors mediate anxiogenic-like behavior, Regul. Pept. 23 Ž1997. 15–21. S.C. Heinrichs, F. Menzaghi, E.M. Pich, K.T. Britton, G.F. Koob, The role of CRF in behavioral aspects of stress, Ann. N. Y. Acad. Sci. 771 Ž1995. 92–104. S.C. Heinrichs, E.M. Pich, K.A. Miczek, K.T. Britton, G.F. Koob, Corticotropin-releasing factor antagonist reduces emotionality in socially defeated rats via direct neurotropic action, Brain Res. 581 Ž1992. 190–197. D.T. Hsu, F.-L. Chen, L.K. Takahashi, N.H. Kalin, Rapid stress-induced elevations in corticotropin-releasing hormone mRNA in rat central amygdala nucleus and hypothalamic paraventricular nucleus: an in situ hybridization analysis, Brain Res. 788 Ž1998. 305–310. K.L. Huhman, B.N. Bunnell, E.H. Mougey, J.L. Meyerhoff, Effects of social conflict on POMC-derived peptides and glucocorticoids in male golden hamsters, Physiol. Behav. 47 Ž1990. 949–956. K.L. Huhman, T.O. Moore, C.F. Ferris, E.H. Mougey, J.L. Meyerhoff, Acute and repeated exposure to social conflict in male golden hamsters: increases in plasma POMC-peptides and cortisol and decreases in plasma testosterone, Horm. Behav. 25 Ž1991. 206–216. K.L. Huhman, T.O. Moore, E.H. Mougey, J.L. Meyerhoff, Hormonal responses to fighting in hamsters: separation of physical and psychological causes, Physiol. Behav. 51 Ž1992. 1083–1086. S. Kollack-Walker, S.J. Watson, H. Akil, Social stress in hamsters: defeat activates specific neurocircuits within the brain, J. Neurosci. 17 Ž1997. 8842–8855. G.F. Koob, S.C. Heinrichs, E. Merlo-Pich, F. Menzaghi, H.A. Baldwin, K.A. Miczek, K.T. Britton, The role of corticotropin-releasing factor in behavioral responses to stress, in: E.B. De Souza, C.B. Nemeroff ŽEds.., Corticotropin-releasing factor: Basic and clinical studies of a neuropeptide, CRC Press, Boca Raton, 1993, pp. 277–295.
128
A.M. Jasnow et al.r Brain Research 846 (1999) 122–128
w22x S.M. Korte, A.H. Korte-Bouws, B. Bohus, G.F. Koob, Effect of corticotropin-releasing factor antagonist on behavioral and neuroendocrine responses during exposure to defensive burying paradigm in rats, Physiol. Behav. 56 Ž1994. 115–120. w23x H. Lehnert, C. Schulz, K. Dieterich, Physiological and neurochemical aspects of corticotropin-releasing factor actions in the brain: the role of the locus coeruleus, Neurochem. Res. 23 Ž1998. 1039–1052. w24x T.W. Lovenberg, D.T. Chalmers, E.B. De Souza, CRF2 a and CRF2b receptor mRNA’s are differentially distributed between the rat central nervous system and peripheral tissues, Endocrinology 136 Ž1995. 4139–4142. w25x J. Lundkvist, Z. Chai, R. Teheranian, H. Hasanvan, T. Bartfai, F. Jenck, U. Widmer, J.-L. Moreau, A non peptidic corticotropin releasing factor receptor antagonist attenuates fever and exhibits anxiolytic-like activity, Eur. J. Pharmacol. 309 Ž1996. 195–200. w26x R.S. Mansbach, E.N. Brooks, Y.L. Chen, Antidepressant-like effects of CP-154,526, a selective CRF1 receptor antagonist, Eur. J. Pharmacol. 323 Ž1997. 21–26. w27x S. Maren, M.S. Fanselow, The amygdala and fear conditioning: has the nut been cracked?, Neuron 16 Ž1996. 237–240. w28x A.P. Martins, R.A. Marras, F.S. Guimaraes, Anxiogenic effect of corticotropin-releasing hormone in the dorsal periaqueductal grey, NeuroReport 8 Ž1997. 3601–3604. w29x W.P. Meehan, W. Tornatzky, K.A. Miczek, Blood pressure via telemetry during social confrontations in rats: effects of clonidine, Physiol. Behav. 58 Ž1995. 81–88. w30x F. Menzaghi, R.L. Howard, S.C. Heinrichs, W. Vale, J. Rivier, G.F. Koob, Characterization of a novel and potent corticotropin-releasing factor antagonist in rats, J. Pharmacol. Exp. Ther. 269 Ž1994. 564–572. w31x R.M. Nowack, J.L. Paradiso, Walker’s Mammals of the World, Johns Hopkins Univ. Press, Baltimore, MD, 1983. w32x E.M. Pich, S.C. Heinrichs, C. Rivier, K.A. Miczek, D.A. Fisher, G.F. Koob, Blockade of pituitary–adrenal axis activation induced by
w33x w34x
w35x
w36x
w37x w38x
w39x
w40x
w41x
peripheral immunoneutralization of corticotropin-releasing factor does not affect the behavioral response to social defeat stress in rats, Psychoneuroendocrinology 18 Ž1993. 495–507. M. Potegal, K.L. Huhman, J.L. Meyerhoff, Conditioned defeat in the Syrian hamster, Behav. Neural Biol. 60 Ž1993. 93–102. R.J. Rodgers, J.C. Cole, Anxiety enhancement in the murine elevated plus maze by immediate prior exposure to social stressors, Physiol. Behav. 53 Ž1993. 383–388. E. Sawchenko, L.W. Swanson, Localization, colocalization, and plasticity of corticotropin-releasing factor immunoreactivity in the brain, Fed. Proc. 44 Ž1985. 221–227. D.W. Schulz, R.S. Mansbach, J. Sprouse, J.P. Braselton, J. Collins, M. Corman, A. Dunaiskis, S. Faraci, A.W. Schmidt, T. Seeger, P. Seymour, F.D. Tingley III, E.N. Winston, Y.L. Chen, J. Heym, CP-154,526: A potent and selective nonpeptide antagonist of corticotropin-releasing factor receptors, Pharmacology 93 Ž1996. 10477– 10482. J.E. Sherman, N.H. Kalin, The effects of i.c.v.-CRH on novelty-induced behavior, Pharmacol. Biochem. Behav. 26 Ž1987. 699–703. G.N. Smagin, R.B. Harris, D.H. Ryan, Corticotropin-releasing factor receptor antagonist infused into the locus coeruleus attenuates immobilization stress-induced defensive withdrawal in rats, Neurosci. Lett. 220 Ž1996. 167–170. R. Sutton, G.F. Koob, M. Le Moal, J. Rivier, W. Vale, Corticotropin-releasing factor ŽCRF. produces behavioral activation in rats, Nature 299 Ž1982. 331–333. R.J. Valentino, S.L. Foote, M.E. Page, The locus coeruleus as a site for integrating corticotropin-releasing factor and noradrenergic mediation of stress responses, Ann. N. Y. Acad. Sci. 697 Ž1993. 173–188. E.L. Webster, D.B. Lewis, D.J. Torpy, E.K. Zachman, K.C. Rice, G.P. Chrousos, In vivo and in vitro characterization of Antalarmin, a nonpeptide corticotropin-releasing hormone ŽCRH. receptor antagonist: suppression of pituitary ACTH release and peripheral inflammation, Endocrinology 137 Ž1996. 5747–5750.