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The effect of glucocorticoids on bradykinesia induced by immobilization stress
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Hormones and Behavior 54 (2008) 41 – 46 www.elsevier.com/locate/yhbeh
The effect of glucocorticoids on bradykinesia induced by immobilization stress Takashi Matsuwaki, Keitaro Yamanouchi, Masugi Nishihara ⁎ Department of Veterinary Physiology, Veterinary Medical Science, The University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo 113-8657, Japan Received 28 August 2007; revised 16 January 2008; accepted 16 January 2008 Available online 7 February 2008
Abstract It is well known that the release of glucocorticoids from the adrenal gland is increased in response to many types of stressors and plays a principal role in stress responses. We have shown that the synthesis of prostaglandins (PGs) in the brain is increased under several stress conditions including immobilization (IMO), and that endogenous glucocorticoids counteract this stress-induced PG synthesis. It was also recently reported that IMO damages dopaminergic (DA) neurons in the substantia nigra (SN), which is known to cause symptoms similar to Parkinson's disease (PD). The present study was therefore undertaken to determine the role of glucocorticoids in modulating the signs of PD induced by IMO. The pole test, in which each mouse was placed head upward at the top of a pole and the time taken to turn downward and to arrive on the floor was recorded, and immunohistochemistry for tyrosine hydroxylase (TH) in the SN were performed to evaluate bradykinesia and injury of DA neurons, respectively. Intact and adrenalectomized (ADX) mice were immobilized for 2 h twice, 1 day apart. Both bradykinesia and a decrease in the number of TH-immunoreactive cells in the SN were observed in ADX mice, but not in intact mice, following IMO. These effects of IMO on ADX mice were restored by treatment with corticosterone or indomethacin, a PG synthesis inhibitor. These results suggest that glucocorticoids play a role in preventing the detrimental effect of IMO on nigral DA neurons and resulting bradykinesia, and that this effect of IMO involves PGmediated mechanisms. © 2008 Elsevier Inc. All rights reserved. Keywords: Bradykinesia; Dopaminergic neurons; Glucocorticoids; Immobilization stress; Prostaglandins; Substantia nigra
Introduction Under stress conditions, large amounts of glucocorticoids are secreted from the adrenal gland, and play a crucial role in maintaining homeostasis (Kapcala et al., 1995). Despite their indispensable roles in ensuring survival, a number of studies have revealed negative effects of glucocorticoids on the central nervous system (CNS), including induction of degeneration of neurons in the hippocampus (reviewed in Conrad, 2006), suppression of neurogenesis (Mirescu and Gould, 2006), and inhibition of brain functions such as memory (de Quervain, 2006). It has also been suggested that hypothalamic control of gonadotropin secretion is suppressed by glucocorticoids (Saketos et al., 1993; McGivern and Redei, 1994; Debus et al., 2002). We have recently reported, however, that increased glu⁎ Corresponding author. Fax: +81 3 5841 8017. E-mail address: [email protected] (M. Nishihara). 0018-506X/$ - see front matter © 2008 Elsevier Inc. All rights reserved. doi:10.1016/j.yhbeh.2008.01.005
cocorticoid secretion has a protective effect on reproductive function under various stress conditions (Matsuwaki et al., 2003, 2004, 2006). In addition, we have also demonstrated that prostaglandins (PGs) synthesized in the brain are a common mediator of stressors in suppressing reproductive function, and that glucocorticoids maintain gonadotropin secretion at least in part by inhibiting cyclooxygenase-2 (COX-2), a PG synthesizing enzyme, in the brain (Matsuwaki et al., 2006). PGs are known to play multiple roles in the CNS including induction of sleep (Hayaishi, 2000) and fever (Ivanov and Romanovsky, 2004; Blatteis et al., 2005). In addition, PGs have recently been implicated in neurodegeneration, as indicated by the association of upregulation of COX-2 levels with neuronal death in the cerebral cortex following immobilization (IMO) stress (Lee et al., 2006). One of the major neurodegenerative diseases is Parkinson's disease (PD), the major pathological characteristic of which is the degeneration of dopaminergic (DA) neurons in the substantia nigra (SN) of
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the midbrain. It is well established that lesions of DA neurons in the SN in experimental animals produced using neurotoxins such as 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) (Bezard et al., 1997; Perry et al., 2005) and 6-hydrodopamine (Schmidt and Beninger, 2006) result in bradykinesia, or slowness of movement, similar to that observed in PD. In a PD model using MPTP, Parkinsonian symptoms are reported to be attenuated by treatment with dexamethasone (KurkowskaJastrzebska et al., 2004), and the authors of that study suggested that an inhibition of the inflammatory process might account for this neuroprotective effect of dexamethasone. We therefore hypothesized that PGs synthesized in the brain in response to some types of stressors could injure nigral DA neurons, and that increased glucocorticoids could inhibit PG synthesis and thereby exert neuroprotective effects. To test this hypothesis, in the present study, we used IMO as a stressor, since it is known to enhance COX-2 expression in the brain (Madrigal et al., 2003; Matsuwaki et al., 2006) as well as to increase glucocorticoid secretion from the adrenal glands (Matsuwaki et al., 2006). Moreover, IMO has recently been reported to induce degeneration of DA neurons in the SN of mice (Kim et al., 2005). Here we evaluated bradykinesia by the pole test and degeneration of DA neurons by immunostaining for tyrosine hydroxylase (TH), a rate-limiting enzyme for DA synthesis, following repeated IMO. Materials and methods Animals Adult (8–10 week-old) male mice of the C57BL/6J strain were used (n = 78). They were maintained under controlled lighting (lights on: 0500–1900 h), and given free access to food and water. Animals (n = 47) were adrenalectomized (ADX) 1 week prior to the experiments. 0.85% saline was given as drinking water to ADX animals. For the pole test, 19 intact and 35 ADX mice were used, parts of which (intact, n = 9; ADX, n = 25) were subjected to IMO in a restraining tube (3 cm in diameter and 11 cm in length) for 2 h beginning 1300 h twice, 1 day apart. Some of the ADX mice were subcutaneously injected with corticosterone (CS, Wako, Osaka, Japan; 5 mg/kg; n = 8) or indomethacin (Wako; 10 mg/kg; n = 9), a PG synthesis inhibitor, just before each episode of IMO. The experiments
were conducted according to the Guidelines for the Care and Use of Laboratory Animals, Graduate School of Agriculture and Life Sciences, the University of Tokyo, and approved by the Institutional Animal Care and Use Committee.
Pole test Severity of bradykinesia was determined by means of the pole test as described by Fujikawa et al. (2005). In brief, each mouse was placed head upward near the top of a wood pole (5 cm in diameter and 100 cm in height) and the time the animals took to turn completely downward and to arrive on the floor were recorded. Pole tests were repeated in triplicate each time and the median value was adopted. The tests were performed 3 times: 1 day prior to the first IMO (1st), and 1 day (2nd) and 7 days (3rd) after the last IMO (n = 9 for intact and n = 25 for ADX mice). The tests were also done 3 times using intact (n = 10) and ADX (n = 10) mice that were not subjected to IMO according to the same time schedule.
Determination of serum corticosterone levels Using different groups of mice subjected to the pole test, blood samples were collected by cardiac puncture from intact mice, intact mice 1 h after the start of IMO, ADX mice, and ADX mice 1 h after CS injection (n = 6 for each group). Serum concentrations of CS were determined by radioimmunoassay with a specific antibody generated in our laboratory using CS conjugated to bovine serum albumin as an antigen (Narita et al., 1994). All samples were measured in a single assay. The assay range was 50–3200 ng/ml, and the intra-assay coefficient of variance was 12.1% for a pooled serum concentration of 387.7 ng/ml.
Immunohistochemistry The day after the 3rd pole test, animals (n = 6 for each group) were anesthetized with pentobarbital sodium (30 mg/kg) and perfused via the left ventricle of the heart with saline followed by 4% paraformaldehyde (PFA) in PBS (0.02 M, pH 7.2). Brains were dissected out and further fixed in the PFA solution overnight, and then soaked in a solution of 30% sucrose in PBS for 3 days. Brains were sectioned at 40 µm thicknesses in a cryostat and one of every 6 slices was used for immunostaining for TH. Free-floating sections were rinsed in PBS for 10 min twice. Sections were then incubated in 0.3% H2O2-PBS for 30 min at room temperature and rinsed in PBS 3 times. Thereafter, sections were incubated in blocking solution (Block Ace, Snow Brand Milk Products Co, Sapporo, Japan) for 2 h. Then, sections were incubated with anti-TH primary antibody (AB-152, Chemicon, Temecula, CA, 1:2000 with 0.3% Triton X-100 in PBS) at 4 °C for 72 h, washed three times with PBS, and processed using a Vectastain ABC kit (Vector Labs, ‘Elite’ ABC reagent, Burlingame, CA). The sections were treated for approximately 3 min in 0.5 mg/ml of diaminobenzidine tetrahydrochloride
Fig. 1. Effects of adrenalectomy (ADX) and treatments with corticosterone (CS) and indomethacin (IND) on the bradykinesia induced by immobilization (IMO). Pole tests were performed 1 day prior to the 1st IMO (1st), and 1 day (2nd) and 7 days (3rd) after the last IMO. The mice were subjected to IMO twice, 1 day apart. CS (5 mg/kg) or IND (10 mg/kg) was subcutaneously injected at the start of each IMO. Each point and vertical line represents the mean and S.E.M. (n = 8–10), respectively. ⁎Significantly different from the values for the other groups at the same time point (P b 0.05, repeated measures ANOVA followed by Tukey–Kramer's test).
T. Matsuwaki et al. / Hormones and Behavior 54 (2008) 41–46 (DAB, Sigma, St. Louis, MO; dissolved in 0.1 M Tris–HCl, with 0.01% hydrogen peroxide and 0.25% nickel), rinsed in 0.1 M Tris–HCl and mounted on glass slides. After dehydration in ethanol and clearing in xylene, the sections were observed under a light microscope (EX51; Olympus, Tokyo, Japan).
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cell. All the TH-ir cells observed in each section were counted and summed up. The cell counting was done two or more times for each section until the count of each time was almost exactly the same.
Statistical analysis TH-immunoreactive (TH-ir) cells counts The number of TH-ir cells was counted under the microscope (×40) on 6 sections at 200 µm intervals. The examiner focused vertically through the various planes of focus in the 40 µm thick section to obtain clear cell shapes, and when a cell had a clear outline of the stained soma, it was regarded as a TH-ir
The data are shown as means and standard error of the mean (S.E.M.). Values were statistically analyzed by repeated measures ANOVA for the results of the pole test and by one-way ANOVA for the results of the other experiments, both of which were followed by Tukey–Kramer's test. Differences were considered significant at P b 0.05.
Fig. 2. Representative images of immunostaining for tyrosine hydroxylase (TH) in the substantia nigra (SN). Corticosterone (CS, 5 mg/kg) or indomethacin (IND, 10 mg/kg) was subcutaneously injected in adrenalectomized (ADX) mice at the start of each immobilization (IMO). Brains of mice were dissected out the day after the last pole test. Scale bars = 200 µm (left column) and 50 µm (right column).
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Results Serum corticosterone levels Serum CS concentration in intact mice subjected to IMO was 326.0 ± 53.7 ng/ml (mean ± S.E.M., n = 6), which was significantly higher than the value (99.5 ± 8.3 ng/ml, n = 6) in intact mice that were not subjected to IMO (P b 0.05, One-way ANOVA followed by Tukey–Kramer's test). In all ADX mice (n = 6), CS levels were below the minimum assay range (50 ng/ml), indicating that the adrenal glands had been successfully removed. In ADX mice treated with CS, serum CS level (538.4 ± 16.5 ng/ml, n = 6) was 1.65 times that in intact mice subjected to IMO (P b 0.05). Pole test Fig. 1 shows the results of pole tests performed for the determination of control of movement and evaluation of the development of bradykinesia. There were no significant differences between intact and ADX mice without IMO in the time taken to turn downward and to arrive on the floor in any of the 3 trials. Although IMO affected neither the time required to turn downward nor the time to reach the floor in intact mice, it significantly prolonged both of those indices in ADX mice. In ADX mice treated with CS or indomethacin, prolongation of these indices was no longer observed, suggesting that CS could counteract the adverse effect of IMO on motor activity and that PGs play a role in the development of the bradykinesia induced by IMO. Immunostaining for TH in SN As shown in Fig. 2, TH-ir cells were distinctively stained in the SN. The number of TH-ir cells in both hemispheres was counted every 6 sections and summed throughout the SN. Results of quantitative analysis of the number of TH-ir cells in
Fig. 3. Number of tyrosine hydroxylase-immunoreactive (TH-ir) cells in the substantia nigra (SN). Corticosterone (CS, 5 mg/kg) or indomethacin (IND, 10 mg/kg) was subcutaneously injected in adrenalectomized (ADX) mice at the start of each immobilization (IMO). Brains of mice were dissected out the day after the last pole test. The sections were cut 40 µm thick and the number of cells was counted every 6 sections and summed throughout the SN. Each column and vertical bar represent the mean and S.E.M. (n = 6), respectively. ⁎Significantly different from the values for the other groups (P b 0.05, one-way ANOVA followed by Tukey–Kramer's test).
the SN are shown in Fig. 3. There was no significant difference in number of TH-ir cells between intact and ADX mice that were not subjected to IMO. While IMO did not affect the number of TH-ir cells in intact mice, it significantly decreased the number of them in ADX mice. Both CS and indomethacin restored TH-ir cell numbers in ADX mice subjected to IMO, suggesting that CS protects DA neurons in the SN from the damage by IMO, and that the effect of IMO on nigral DA neurons may involve PG-mediated mechanisms. Discussion The pole test is an ethopharmacological method of analysis developed for determination of severity of bradykinesia, or slowness of movement, in rats and mice (Fujikawa et al., 2005). Development of bradykinesia is reflected by prolongation of the time taken to turn downward and to arrive on the floor. In the present study, both of these indices were significantly prolonged by IMO in ADX mice, while they were not affected in adrenalintact mice. This behavioral effect of IMO is consistent with the histological observation that IMO significantly decreased the number of TH-ir neurons in the SN in ADX mice, but not in intact mice. ADX alone affected neither motor activity nor the number of TH-ir neurons, indicating that adrenal hormones may not be involved in maintaining them under non-stressful conditions. Kim et al. (2005) applied IMO repeatedly to intact ICR mice and found signs of oxidative damages in the nigrostriatal system 2 h after the last IMO, which was followed by degeneration of the nigral DA neurons. Thus, the decreased number of TH-ir cells observed in the present study was probably due to the loss of DA neurons rather than decreased amount of TH in individual cells under the sensitivity of the antibody used. In any case, our results support the notion that repeated IMO causes damages to DA neurons in the SN, to which ADX animals were more susceptible. In the present study, serum levels of glucocorticoids were markedly increased in response to IMO. Glucocorticoids seem to have both negative and positive effects on neurons. Glucocorticoids were generally reported to negatively affect the survival of neurons (reviewed in Conrad, 2006), while some groups have reported the importance of glucocorticoids for survival of neurons in some regions of the brain including the hippocampus (Sloviter et al., 1989; Hu et al., 1997) and memory consolidation (Roozendaal et al., 1999). In the present study, exogenous CS, which did not exceed too far from stressinduced CS levels, counteracted the detrimental effects of IMO on nigral DA neurons in ADX mice, demonstrating neuroprotective effects of glucocorticoids at least under the stress condition adopted here. In addition, CS restored ability to control the body movement of ADX mice subjected to IMO to the same level as that in both intact and ADX animals without IMO. In our previous studies, we determined the protective effect of glucocorticoids on the hypothalamic function controlling gonadotropin secretion under infectious, metabolic and restraint stress conditions (Matsuwaki et al., 2003, 2004, 2006). These findings together suggest that endogenous glucocorticoids secreted in response to stressors are involved in maintaining some functions of the brain.
T. Matsuwaki et al. / Hormones and Behavior 54 (2008) 41–46
We have previously demonstrated that PGs synthesized in the brain probably play roles as common mediators of some stressors (Matsuwaki et al., 2006). As do many other types of stressors (Shohami et al., 1985), IMO has been reported to induce COX-2 in the brain (Madrigal et al., 2003). IMO was also reported to trigger the secretion of many types of neurotransmitters and cytokines, and thus to lead to neurodegeneration (Lee et al., 2006). Furthermore, MPTP and some other chemicals were reported to induce COX-2 expression in the SN (de Meira Santos Lima et al., 2006). In the present study, indomethacin, an inhibitor of COX-2, restored motor ability and prevented the decrease in the number of DA neurons in the SN following IMO. These results suggest that PGs synthesized in response to IMO play a major role in the damage of nigral DA neurons and the resultant bradykinesia. These findings correspond to those obtained by Chen et al. (2003), who reported that inflammatory factors are among the major causes of degeneration of DA neurons in the SN of PD model animals. In addition, it has been reported that PG-induced neurodegeneration is associated with increased levels of oxidants (Yan et al., 2005), and that degeneration of DA neurons by IMO is due to the oxidative injury (Kim et al., 2005). These reports support the hypothesis that PGs in the brain mediate the detrimental effect of IMO on nigral DA neurons. The synthesis of PGs is known to be inhibited by glucocorticoids (Sudlow et al., 1996; Kim et al., 2001), and in our previous study glucocorticoids effectively suppressed COX-2 expression in the brain under stress conditions (Matsuwaki et al., 2006). It thus appears that the neuroprotective effects of glucocorticoids observed in the present study can be attributed to suppression of PG synthesis in the brain. In support of this, it has been reported that the receptors for glucocorticoids are located in the SN (Czyrak and Chocyk, 2001), and that glucocorticoid receptor deficiency increases the vulnerability of DA neurons in the SN to cytotoxic chemicals (Morale et al., 2003). Notably, the responsiveness of the hypothalamic-pituitary-adrenal (HPA) axis to stressors is attenuated in PD patients (Volpi et al., 1991, 1993). Together with these findings, the results of the present study suggest that dysfunction of the HPA axis could enhance PG synthesis in the brain, with resultant degeneration of nigral DA neurons and bradykinesia resembling that in PD. In conclusion, the present study demonstrated that IMO induced bradykinesia as well as a decrease in the number of TH-ir cells in the SN in ADX mice, and that glucocorticoids prevented these detrimental effects of IMO. In addition, it is suggested that PGs produced in the brain play roles in the mechanisms by which IMO affects neuronal histology and motor activity, and that neuroprotective effects of glucocorticoids are exerted at least in part via inhibition of PG synthesis in the brain. Acknowledgments This work was supported in part by a Grant-in-Aid for Scientific Research (17208025 to MN) and Research Fellowships for Young Scientists (1611663 to TM) from the Japan Society for the Promotion of Science.
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References Bezard, E., Dovero, S., Bioulac, B., Gross, C., 1997. Effects of different schedules of MPTP administration on dopaminergic neurodegeneration in mice. Exp. Neurol. 148, 288–292. Blatteis, C., Li, S., Li, Z., Feleder, C., Perlik, V., 2005. Cytokines, PGE2 and endotoxic fever: a re-assessment. Prostaglandins Other Lipid Mediat. 76, 1–18. Chen, H., Zhang, S., Hernán, M., Schwarzschild, M., Willett, W., Colditz, G., Speizer, F., Ascherio, A., 2003. Nonsteroidal anti-inflammatory drugs and the risk of Parkinson disease. Arch. Neurol. 60, 1059–1064. Conrad, C.D., 2006. What is the functional significance of chronic stressinduced CA3 dendritic retraction within the hippocampus? Behav. Cogn. Neurosci. Rev. 5, 41–60. Czyrak, A., Chocyk, A., 2001. Search for the presence of glucocorticoid receptors in dopaminergic neurons of rat ventral tegmental area and substantia nigra. Pol. J. Pharmacol. 53, 681–684. Debus, N., Breen, K.M., Barrell, G.K., Billings, H.J., Brown, M., Young, E.A., Karsch, F.J., 2002. Does cortisol mediate endotoxin-induced inhibition of pulsatile luteinizing hormone and gonadotropin-releasing hormone secretion? Endocrinology 143, 3748–3758. de Meira Santos Lima, M., Braga Reksidler, A., Marques Zanata, S., Bueno Machado, H., Tufik, S., Vital, M.A., 2006. Different parkinsonism models produce a time-dependent induction of COX-2 in the substantia nigra of rats. Brain Res. 1101, 117–125. de Quervain, D.J., 2006. Glucocorticoid-induced inhibition of memory retrieval: implications for posttraumatic stress disorder. Ann. N. Y. Acad. Sci. 1071, 216–220. Fujikawa, T., Miguchi, S., Kanada, N., Nakai, N., Ogata, M., Suzuki, I., Nakashima, K., 2005. Acanthopanax senticosus Harms as a prophylactic for MPTP-induced Parkinson's disease in rats. J. Ethnopharmacol. 97, 375–381. Hayaishi, O., 2000. Molecular mechanisms of sleep–wake regulation: a role of prostaglandin D2. Philos. Trans. R. Soc. Lond., B. Biol. Sci. 355, 275–280. Hu, Z., Yuri, K., Ozawa, H., Lu, H., Yang, Y., Ito, T., Kawata, M., 1997. Adrenalectomy-induced granule cell death is predicated on the disappearance of glucocorticoid receptor immunoreactivity in the rat hippocampal granule cell layer. Brain Res. 778, 293–301. Ivanov, A., Romanovsky, A., 2004. Prostaglandin E2 as a mediator of fever: synthesis and catabolism. Front. Biosci. 9, 1977–1993. Kapcala, L.P., Chautard, T., Eskay, R.L., 1995. The protective role of the hypothalamic-pituitary-adrenal axis against lethality produced by immune, infectious, and inflammatory stress. Ann. N. Y. Acad. Sci. 771, 419–437. Kim, S., Choi, J., Chang, J., Kim, S., Hwang, O., 2005. Immobilization stress causes increases in tetrahydrobiopterin, dopamine, and neuromelanin and oxidative damage in the nigrostriatal system. J. Neurochem. 95, 89–98. Kim, S., Rhee, H., Ko, J., Kim, Y., Kim, H., Yang, J., Choi, E., Na, D., 2001. Inhibition of cytosolic phospholipase A(2) by annexin I — specific interaction model and mapping of the interaction site. J. Biol. Chem.. 276, 15712–15719. Kurkowska-Jastrzebska, I., Litwin, T., Joniec, I., Ciesielska, A., Przybyłkowski, A., Członkowski, A., Członkowska, A., 2004. Dexamethasone protects against dopaminergic neurons damage in a mouse model of Parkinson's disease. Int. Immunopharmacol. 4, 1307–1318. Lee, Y.J., Choi, B., Lee, E.H., Choi, K.S., Sohn, S., 2006. Immobilization stress induces cell death through production of reactive oxygen species in the mouse cerebral cortex. Neurosci. Lett. 392, 27–31. Madrigal, J.L., Moro, M.A., Lizasoain, I., Lorenzo, P., Fernandez, A.P., Rodrigo, J., Bosca, L., Leza, J.C., 2003. Induction of cyclooxygenase-2 accounts for restraint stress-induced oxidative status in rat brain. Neuropsychopharmacology 28, 1579–1588. Matsuwaki, T., Kayasuga, Y., Yamanouchi, K., Nishihara, M., 2006. Maintenance of gonadotropin secretion by glucocorticoids under stress conditions through the inhibition of prostaglandin synthesis in the brain. Endocrinology 147, 1087–1093. Matsuwaki, T., Suzuki, M., Yamanouchi, K., Nishihara, M., 2004. Glucocorticoid counteracts the suppressive effect of tumor necrosis factor-α on the surge of luteinizing hormone secretion in rats. J. Endocrinol. 181, 509–513. Matsuwaki, T., Watanabe, E., Suzuki, M., Yamanouchi, K., Nishihara, M., 2003. Glucocorticoid maintains pulsatile secretion of luteinizing hormone under infectious stress condition. Endocrinology 144, 3477–3482.
46
T. Matsuwaki et al. / Hormones and Behavior 54 (2008) 41–46
McGivern, R., Redei, E., 1994. Adrenalectomy reverses stress-induced suppression of luteinizing hormone secretion in long-term ovariectomized rats. Physiol. Behav. 55, 1147–1150. Mirescu, C., Gould, E., 2006. Stress and adult neurogenesis. Hippocampus 16, 233–238. Morale, M., Serra, P., Delogu, M., Migheli, R., Rocchitta, G., Tirolo, C., Caniglia, S., Testa, N., L'Episcopo, F., Gennuso, F., Scoto, G., Barden, N., Miele, E., Desole, M., Marchetti, B., 2003. Glucocorticoid receptor deficiency increases vulnerability of the nigrostriatal dopaminergic system: critical role of glial nitric oxide. FASEB J., 18, 164–166. Narita, K., Nishihara, M., Takahashi, M., 1994. Concomitant regulation of running activity and metabolic change by the ventromedial nucleus of the hypothalamus. Brain Res. 642, 290–296. Perry, J., Hipólide, D., Tufik, S., Martins, R., Da Cunha, C., Andreatini, R., Vital, M., 2005. Intra-nigral MPTP lesion in rats: behavioral and autoradiography studies. Exp. Neurol. 195, 322–329. Roozendaal, B., Nguyen, B.T., Power, A.E., McGaugh, J.L., 1999. Basolateral amygdala noradrenergic influence enables enhancement of memory consolidation induced by hippocampal glucocorticoid receptor activation. Proc. Natl. Acad. Sci. U. S. A. 96, 11642–11647. Saketos, M., Sharma, N., Santoro, N., 1993. Suppression of the hypothalamicpituitary-ovarian axis in normal women by glucocorticoids. Biol. Reprod. 49, 1270–1276.
Schmidt, W.J., Beninger, R.J., 2006. Behavioural sensitization in addiction, schizophrenia, Parkinson's disease and dyskinesia. Neurotox. Res. 10, 161–166. Shohami, E., Globus, M., Weidenfeld, J., 1985. Regional distribution of prostanoids in rat brain: effect of insulin and 2-deoxyglucose. Exp. Brain Res. 61, 87–90. Sloviter, R.S., Valiquette, G., Abrams, G.M., Ronk, E.C., Sollas, A.L., Paul, L.A., Neubort, S., 1989. Selective loss of hippocampal granule cells in the mature rat brain after adrenalectomy. Science 243, 535–538. Sudlow, A., Carey, F., Forder, R., Rothwell, N., 1996. The role of lipocortin-1 in dexamethasone-induced suppression of PGE2 and TNF alpha release from human peripheral blood mononuclear cells. Br. J. Pharmacol. 117, 1449–1456. Volpi, R., Caffarra, P., Marcato, A., Scaglioni, A., Maestri, D., Delsignore, R., Chiodera, P., Coiro, V., 1991. Reduced ACTH/cortisol responses to naloxone in men with Parkinson's disease. J. Neural. Transm., Parkinson's Dis. Dement. Sect. 3, 127–132. Volpi, R., Caffarra, P., Scaglioni, A., Saginario, A., Maestri, D., Vourna, S., Vescovi, P., Chiodera, P., Coiro, V., 1993. Lack of ACTH/cortisol and GH responses to intravenously-infused substance P in Parkinson's disease. J. Neural Transm., Parkinson's Dis. Dement. Sect. 6, 99–107. Yan, X.D., Kumar, B., Nahreini, P., Hanson, A.J., Prasad, J.E., Prasad, K.N., 2005. Prostaglandin-induced neurodegeneration is associated with increased levels of oxidative markers and reduced by a mixture of antioxidants. J. eurosci. Res. 81, 85–90.
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The effect of glucocorticoids on bradykinesia induced by immobilization stress Takashi Matsuwaki, Keitaro Yamanouchi, Masugi Nishihara ⁎ Department of Veterinary Physiology, Veterinary Medical Science, The University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo 113-8657, Japan Received 28 August 2007; revised 16 January 2008; accepted 16 January 2008 Available online 7 February 2008
Abstract It is well known that the release of glucocorticoids from the adrenal gland is increased in response to many types of stressors and plays a principal role in stress responses. We have shown that the synthesis of prostaglandins (PGs) in the brain is increased under several stress conditions including immobilization (IMO), and that endogenous glucocorticoids counteract this stress-induced PG synthesis. It was also recently reported that IMO damages dopaminergic (DA) neurons in the substantia nigra (SN), which is known to cause symptoms similar to Parkinson's disease (PD). The present study was therefore undertaken to determine the role of glucocorticoids in modulating the signs of PD induced by IMO. The pole test, in which each mouse was placed head upward at the top of a pole and the time taken to turn downward and to arrive on the floor was recorded, and immunohistochemistry for tyrosine hydroxylase (TH) in the SN were performed to evaluate bradykinesia and injury of DA neurons, respectively. Intact and adrenalectomized (ADX) mice were immobilized for 2 h twice, 1 day apart. Both bradykinesia and a decrease in the number of TH-immunoreactive cells in the SN were observed in ADX mice, but not in intact mice, following IMO. These effects of IMO on ADX mice were restored by treatment with corticosterone or indomethacin, a PG synthesis inhibitor. These results suggest that glucocorticoids play a role in preventing the detrimental effect of IMO on nigral DA neurons and resulting bradykinesia, and that this effect of IMO involves PGmediated mechanisms. © 2008 Elsevier Inc. All rights reserved. Keywords: Bradykinesia; Dopaminergic neurons; Glucocorticoids; Immobilization stress; Prostaglandins; Substantia nigra
Introduction Under stress conditions, large amounts of glucocorticoids are secreted from the adrenal gland, and play a crucial role in maintaining homeostasis (Kapcala et al., 1995). Despite their indispensable roles in ensuring survival, a number of studies have revealed negative effects of glucocorticoids on the central nervous system (CNS), including induction of degeneration of neurons in the hippocampus (reviewed in Conrad, 2006), suppression of neurogenesis (Mirescu and Gould, 2006), and inhibition of brain functions such as memory (de Quervain, 2006). It has also been suggested that hypothalamic control of gonadotropin secretion is suppressed by glucocorticoids (Saketos et al., 1993; McGivern and Redei, 1994; Debus et al., 2002). We have recently reported, however, that increased glu⁎ Corresponding author. Fax: +81 3 5841 8017. E-mail address: [email protected] (M. Nishihara). 0018-506X/$ - see front matter © 2008 Elsevier Inc. All rights reserved. doi:10.1016/j.yhbeh.2008.01.005
cocorticoid secretion has a protective effect on reproductive function under various stress conditions (Matsuwaki et al., 2003, 2004, 2006). In addition, we have also demonstrated that prostaglandins (PGs) synthesized in the brain are a common mediator of stressors in suppressing reproductive function, and that glucocorticoids maintain gonadotropin secretion at least in part by inhibiting cyclooxygenase-2 (COX-2), a PG synthesizing enzyme, in the brain (Matsuwaki et al., 2006). PGs are known to play multiple roles in the CNS including induction of sleep (Hayaishi, 2000) and fever (Ivanov and Romanovsky, 2004; Blatteis et al., 2005). In addition, PGs have recently been implicated in neurodegeneration, as indicated by the association of upregulation of COX-2 levels with neuronal death in the cerebral cortex following immobilization (IMO) stress (Lee et al., 2006). One of the major neurodegenerative diseases is Parkinson's disease (PD), the major pathological characteristic of which is the degeneration of dopaminergic (DA) neurons in the substantia nigra (SN) of
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the midbrain. It is well established that lesions of DA neurons in the SN in experimental animals produced using neurotoxins such as 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) (Bezard et al., 1997; Perry et al., 2005) and 6-hydrodopamine (Schmidt and Beninger, 2006) result in bradykinesia, or slowness of movement, similar to that observed in PD. In a PD model using MPTP, Parkinsonian symptoms are reported to be attenuated by treatment with dexamethasone (KurkowskaJastrzebska et al., 2004), and the authors of that study suggested that an inhibition of the inflammatory process might account for this neuroprotective effect of dexamethasone. We therefore hypothesized that PGs synthesized in the brain in response to some types of stressors could injure nigral DA neurons, and that increased glucocorticoids could inhibit PG synthesis and thereby exert neuroprotective effects. To test this hypothesis, in the present study, we used IMO as a stressor, since it is known to enhance COX-2 expression in the brain (Madrigal et al., 2003; Matsuwaki et al., 2006) as well as to increase glucocorticoid secretion from the adrenal glands (Matsuwaki et al., 2006). Moreover, IMO has recently been reported to induce degeneration of DA neurons in the SN of mice (Kim et al., 2005). Here we evaluated bradykinesia by the pole test and degeneration of DA neurons by immunostaining for tyrosine hydroxylase (TH), a rate-limiting enzyme for DA synthesis, following repeated IMO. Materials and methods Animals Adult (8–10 week-old) male mice of the C57BL/6J strain were used (n = 78). They were maintained under controlled lighting (lights on: 0500–1900 h), and given free access to food and water. Animals (n = 47) were adrenalectomized (ADX) 1 week prior to the experiments. 0.85% saline was given as drinking water to ADX animals. For the pole test, 19 intact and 35 ADX mice were used, parts of which (intact, n = 9; ADX, n = 25) were subjected to IMO in a restraining tube (3 cm in diameter and 11 cm in length) for 2 h beginning 1300 h twice, 1 day apart. Some of the ADX mice were subcutaneously injected with corticosterone (CS, Wako, Osaka, Japan; 5 mg/kg; n = 8) or indomethacin (Wako; 10 mg/kg; n = 9), a PG synthesis inhibitor, just before each episode of IMO. The experiments
were conducted according to the Guidelines for the Care and Use of Laboratory Animals, Graduate School of Agriculture and Life Sciences, the University of Tokyo, and approved by the Institutional Animal Care and Use Committee.
Pole test Severity of bradykinesia was determined by means of the pole test as described by Fujikawa et al. (2005). In brief, each mouse was placed head upward near the top of a wood pole (5 cm in diameter and 100 cm in height) and the time the animals took to turn completely downward and to arrive on the floor were recorded. Pole tests were repeated in triplicate each time and the median value was adopted. The tests were performed 3 times: 1 day prior to the first IMO (1st), and 1 day (2nd) and 7 days (3rd) after the last IMO (n = 9 for intact and n = 25 for ADX mice). The tests were also done 3 times using intact (n = 10) and ADX (n = 10) mice that were not subjected to IMO according to the same time schedule.
Determination of serum corticosterone levels Using different groups of mice subjected to the pole test, blood samples were collected by cardiac puncture from intact mice, intact mice 1 h after the start of IMO, ADX mice, and ADX mice 1 h after CS injection (n = 6 for each group). Serum concentrations of CS were determined by radioimmunoassay with a specific antibody generated in our laboratory using CS conjugated to bovine serum albumin as an antigen (Narita et al., 1994). All samples were measured in a single assay. The assay range was 50–3200 ng/ml, and the intra-assay coefficient of variance was 12.1% for a pooled serum concentration of 387.7 ng/ml.
Immunohistochemistry The day after the 3rd pole test, animals (n = 6 for each group) were anesthetized with pentobarbital sodium (30 mg/kg) and perfused via the left ventricle of the heart with saline followed by 4% paraformaldehyde (PFA) in PBS (0.02 M, pH 7.2). Brains were dissected out and further fixed in the PFA solution overnight, and then soaked in a solution of 30% sucrose in PBS for 3 days. Brains were sectioned at 40 µm thicknesses in a cryostat and one of every 6 slices was used for immunostaining for TH. Free-floating sections were rinsed in PBS for 10 min twice. Sections were then incubated in 0.3% H2O2-PBS for 30 min at room temperature and rinsed in PBS 3 times. Thereafter, sections were incubated in blocking solution (Block Ace, Snow Brand Milk Products Co, Sapporo, Japan) for 2 h. Then, sections were incubated with anti-TH primary antibody (AB-152, Chemicon, Temecula, CA, 1:2000 with 0.3% Triton X-100 in PBS) at 4 °C for 72 h, washed three times with PBS, and processed using a Vectastain ABC kit (Vector Labs, ‘Elite’ ABC reagent, Burlingame, CA). The sections were treated for approximately 3 min in 0.5 mg/ml of diaminobenzidine tetrahydrochloride
Fig. 1. Effects of adrenalectomy (ADX) and treatments with corticosterone (CS) and indomethacin (IND) on the bradykinesia induced by immobilization (IMO). Pole tests were performed 1 day prior to the 1st IMO (1st), and 1 day (2nd) and 7 days (3rd) after the last IMO. The mice were subjected to IMO twice, 1 day apart. CS (5 mg/kg) or IND (10 mg/kg) was subcutaneously injected at the start of each IMO. Each point and vertical line represents the mean and S.E.M. (n = 8–10), respectively. ⁎Significantly different from the values for the other groups at the same time point (P b 0.05, repeated measures ANOVA followed by Tukey–Kramer's test).
T. Matsuwaki et al. / Hormones and Behavior 54 (2008) 41–46 (DAB, Sigma, St. Louis, MO; dissolved in 0.1 M Tris–HCl, with 0.01% hydrogen peroxide and 0.25% nickel), rinsed in 0.1 M Tris–HCl and mounted on glass slides. After dehydration in ethanol and clearing in xylene, the sections were observed under a light microscope (EX51; Olympus, Tokyo, Japan).
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cell. All the TH-ir cells observed in each section were counted and summed up. The cell counting was done two or more times for each section until the count of each time was almost exactly the same.
Statistical analysis TH-immunoreactive (TH-ir) cells counts The number of TH-ir cells was counted under the microscope (×40) on 6 sections at 200 µm intervals. The examiner focused vertically through the various planes of focus in the 40 µm thick section to obtain clear cell shapes, and when a cell had a clear outline of the stained soma, it was regarded as a TH-ir
The data are shown as means and standard error of the mean (S.E.M.). Values were statistically analyzed by repeated measures ANOVA for the results of the pole test and by one-way ANOVA for the results of the other experiments, both of which were followed by Tukey–Kramer's test. Differences were considered significant at P b 0.05.
Fig. 2. Representative images of immunostaining for tyrosine hydroxylase (TH) in the substantia nigra (SN). Corticosterone (CS, 5 mg/kg) or indomethacin (IND, 10 mg/kg) was subcutaneously injected in adrenalectomized (ADX) mice at the start of each immobilization (IMO). Brains of mice were dissected out the day after the last pole test. Scale bars = 200 µm (left column) and 50 µm (right column).
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Results Serum corticosterone levels Serum CS concentration in intact mice subjected to IMO was 326.0 ± 53.7 ng/ml (mean ± S.E.M., n = 6), which was significantly higher than the value (99.5 ± 8.3 ng/ml, n = 6) in intact mice that were not subjected to IMO (P b 0.05, One-way ANOVA followed by Tukey–Kramer's test). In all ADX mice (n = 6), CS levels were below the minimum assay range (50 ng/ml), indicating that the adrenal glands had been successfully removed. In ADX mice treated with CS, serum CS level (538.4 ± 16.5 ng/ml, n = 6) was 1.65 times that in intact mice subjected to IMO (P b 0.05). Pole test Fig. 1 shows the results of pole tests performed for the determination of control of movement and evaluation of the development of bradykinesia. There were no significant differences between intact and ADX mice without IMO in the time taken to turn downward and to arrive on the floor in any of the 3 trials. Although IMO affected neither the time required to turn downward nor the time to reach the floor in intact mice, it significantly prolonged both of those indices in ADX mice. In ADX mice treated with CS or indomethacin, prolongation of these indices was no longer observed, suggesting that CS could counteract the adverse effect of IMO on motor activity and that PGs play a role in the development of the bradykinesia induced by IMO. Immunostaining for TH in SN As shown in Fig. 2, TH-ir cells were distinctively stained in the SN. The number of TH-ir cells in both hemispheres was counted every 6 sections and summed throughout the SN. Results of quantitative analysis of the number of TH-ir cells in
Fig. 3. Number of tyrosine hydroxylase-immunoreactive (TH-ir) cells in the substantia nigra (SN). Corticosterone (CS, 5 mg/kg) or indomethacin (IND, 10 mg/kg) was subcutaneously injected in adrenalectomized (ADX) mice at the start of each immobilization (IMO). Brains of mice were dissected out the day after the last pole test. The sections were cut 40 µm thick and the number of cells was counted every 6 sections and summed throughout the SN. Each column and vertical bar represent the mean and S.E.M. (n = 6), respectively. ⁎Significantly different from the values for the other groups (P b 0.05, one-way ANOVA followed by Tukey–Kramer's test).
the SN are shown in Fig. 3. There was no significant difference in number of TH-ir cells between intact and ADX mice that were not subjected to IMO. While IMO did not affect the number of TH-ir cells in intact mice, it significantly decreased the number of them in ADX mice. Both CS and indomethacin restored TH-ir cell numbers in ADX mice subjected to IMO, suggesting that CS protects DA neurons in the SN from the damage by IMO, and that the effect of IMO on nigral DA neurons may involve PG-mediated mechanisms. Discussion The pole test is an ethopharmacological method of analysis developed for determination of severity of bradykinesia, or slowness of movement, in rats and mice (Fujikawa et al., 2005). Development of bradykinesia is reflected by prolongation of the time taken to turn downward and to arrive on the floor. In the present study, both of these indices were significantly prolonged by IMO in ADX mice, while they were not affected in adrenalintact mice. This behavioral effect of IMO is consistent with the histological observation that IMO significantly decreased the number of TH-ir neurons in the SN in ADX mice, but not in intact mice. ADX alone affected neither motor activity nor the number of TH-ir neurons, indicating that adrenal hormones may not be involved in maintaining them under non-stressful conditions. Kim et al. (2005) applied IMO repeatedly to intact ICR mice and found signs of oxidative damages in the nigrostriatal system 2 h after the last IMO, which was followed by degeneration of the nigral DA neurons. Thus, the decreased number of TH-ir cells observed in the present study was probably due to the loss of DA neurons rather than decreased amount of TH in individual cells under the sensitivity of the antibody used. In any case, our results support the notion that repeated IMO causes damages to DA neurons in the SN, to which ADX animals were more susceptible. In the present study, serum levels of glucocorticoids were markedly increased in response to IMO. Glucocorticoids seem to have both negative and positive effects on neurons. Glucocorticoids were generally reported to negatively affect the survival of neurons (reviewed in Conrad, 2006), while some groups have reported the importance of glucocorticoids for survival of neurons in some regions of the brain including the hippocampus (Sloviter et al., 1989; Hu et al., 1997) and memory consolidation (Roozendaal et al., 1999). In the present study, exogenous CS, which did not exceed too far from stressinduced CS levels, counteracted the detrimental effects of IMO on nigral DA neurons in ADX mice, demonstrating neuroprotective effects of glucocorticoids at least under the stress condition adopted here. In addition, CS restored ability to control the body movement of ADX mice subjected to IMO to the same level as that in both intact and ADX animals without IMO. In our previous studies, we determined the protective effect of glucocorticoids on the hypothalamic function controlling gonadotropin secretion under infectious, metabolic and restraint stress conditions (Matsuwaki et al., 2003, 2004, 2006). These findings together suggest that endogenous glucocorticoids secreted in response to stressors are involved in maintaining some functions of the brain.
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We have previously demonstrated that PGs synthesized in the brain probably play roles as common mediators of some stressors (Matsuwaki et al., 2006). As do many other types of stressors (Shohami et al., 1985), IMO has been reported to induce COX-2 in the brain (Madrigal et al., 2003). IMO was also reported to trigger the secretion of many types of neurotransmitters and cytokines, and thus to lead to neurodegeneration (Lee et al., 2006). Furthermore, MPTP and some other chemicals were reported to induce COX-2 expression in the SN (de Meira Santos Lima et al., 2006). In the present study, indomethacin, an inhibitor of COX-2, restored motor ability and prevented the decrease in the number of DA neurons in the SN following IMO. These results suggest that PGs synthesized in response to IMO play a major role in the damage of nigral DA neurons and the resultant bradykinesia. These findings correspond to those obtained by Chen et al. (2003), who reported that inflammatory factors are among the major causes of degeneration of DA neurons in the SN of PD model animals. In addition, it has been reported that PG-induced neurodegeneration is associated with increased levels of oxidants (Yan et al., 2005), and that degeneration of DA neurons by IMO is due to the oxidative injury (Kim et al., 2005). These reports support the hypothesis that PGs in the brain mediate the detrimental effect of IMO on nigral DA neurons. The synthesis of PGs is known to be inhibited by glucocorticoids (Sudlow et al., 1996; Kim et al., 2001), and in our previous study glucocorticoids effectively suppressed COX-2 expression in the brain under stress conditions (Matsuwaki et al., 2006). It thus appears that the neuroprotective effects of glucocorticoids observed in the present study can be attributed to suppression of PG synthesis in the brain. In support of this, it has been reported that the receptors for glucocorticoids are located in the SN (Czyrak and Chocyk, 2001), and that glucocorticoid receptor deficiency increases the vulnerability of DA neurons in the SN to cytotoxic chemicals (Morale et al., 2003). Notably, the responsiveness of the hypothalamic-pituitary-adrenal (HPA) axis to stressors is attenuated in PD patients (Volpi et al., 1991, 1993). Together with these findings, the results of the present study suggest that dysfunction of the HPA axis could enhance PG synthesis in the brain, with resultant degeneration of nigral DA neurons and bradykinesia resembling that in PD. In conclusion, the present study demonstrated that IMO induced bradykinesia as well as a decrease in the number of TH-ir cells in the SN in ADX mice, and that glucocorticoids prevented these detrimental effects of IMO. In addition, it is suggested that PGs produced in the brain play roles in the mechanisms by which IMO affects neuronal histology and motor activity, and that neuroprotective effects of glucocorticoids are exerted at least in part via inhibition of PG synthesis in the brain. Acknowledgments This work was supported in part by a Grant-in-Aid for Scientific Research (17208025 to MN) and Research Fellowships for Young Scientists (1611663 to TM) from the Japan Society for the Promotion of Science.
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References Bezard, E., Dovero, S., Bioulac, B., Gross, C., 1997. Effects of different schedules of MPTP administration on dopaminergic neurodegeneration in mice. Exp. Neurol. 148, 288–292. Blatteis, C., Li, S., Li, Z., Feleder, C., Perlik, V., 2005. Cytokines, PGE2 and endotoxic fever: a re-assessment. Prostaglandins Other Lipid Mediat. 76, 1–18. Chen, H., Zhang, S., Hernán, M., Schwarzschild, M., Willett, W., Colditz, G., Speizer, F., Ascherio, A., 2003. Nonsteroidal anti-inflammatory drugs and the risk of Parkinson disease. Arch. Neurol. 60, 1059–1064. Conrad, C.D., 2006. What is the functional significance of chronic stressinduced CA3 dendritic retraction within the hippocampus? Behav. Cogn. Neurosci. Rev. 5, 41–60. Czyrak, A., Chocyk, A., 2001. Search for the presence of glucocorticoid receptors in dopaminergic neurons of rat ventral tegmental area and substantia nigra. Pol. J. Pharmacol. 53, 681–684. Debus, N., Breen, K.M., Barrell, G.K., Billings, H.J., Brown, M., Young, E.A., Karsch, F.J., 2002. Does cortisol mediate endotoxin-induced inhibition of pulsatile luteinizing hormone and gonadotropin-releasing hormone secretion? Endocrinology 143, 3748–3758. de Meira Santos Lima, M., Braga Reksidler, A., Marques Zanata, S., Bueno Machado, H., Tufik, S., Vital, M.A., 2006. Different parkinsonism models produce a time-dependent induction of COX-2 in the substantia nigra of rats. Brain Res. 1101, 117–125. de Quervain, D.J., 2006. Glucocorticoid-induced inhibition of memory retrieval: implications for posttraumatic stress disorder. Ann. N. Y. Acad. Sci. 1071, 216–220. Fujikawa, T., Miguchi, S., Kanada, N., Nakai, N., Ogata, M., Suzuki, I., Nakashima, K., 2005. Acanthopanax senticosus Harms as a prophylactic for MPTP-induced Parkinson's disease in rats. J. Ethnopharmacol. 97, 375–381. Hayaishi, O., 2000. Molecular mechanisms of sleep–wake regulation: a role of prostaglandin D2. Philos. Trans. R. Soc. Lond., B. Biol. Sci. 355, 275–280. Hu, Z., Yuri, K., Ozawa, H., Lu, H., Yang, Y., Ito, T., Kawata, M., 1997. Adrenalectomy-induced granule cell death is predicated on the disappearance of glucocorticoid receptor immunoreactivity in the rat hippocampal granule cell layer. Brain Res. 778, 293–301. Ivanov, A., Romanovsky, A., 2004. Prostaglandin E2 as a mediator of fever: synthesis and catabolism. Front. Biosci. 9, 1977–1993. Kapcala, L.P., Chautard, T., Eskay, R.L., 1995. The protective role of the hypothalamic-pituitary-adrenal axis against lethality produced by immune, infectious, and inflammatory stress. Ann. N. Y. Acad. Sci. 771, 419–437. Kim, S., Choi, J., Chang, J., Kim, S., Hwang, O., 2005. Immobilization stress causes increases in tetrahydrobiopterin, dopamine, and neuromelanin and oxidative damage in the nigrostriatal system. J. Neurochem. 95, 89–98. Kim, S., Rhee, H., Ko, J., Kim, Y., Kim, H., Yang, J., Choi, E., Na, D., 2001. Inhibition of cytosolic phospholipase A(2) by annexin I — specific interaction model and mapping of the interaction site. J. Biol. Chem.. 276, 15712–15719. Kurkowska-Jastrzebska, I., Litwin, T., Joniec, I., Ciesielska, A., Przybyłkowski, A., Członkowski, A., Członkowska, A., 2004. Dexamethasone protects against dopaminergic neurons damage in a mouse model of Parkinson's disease. Int. Immunopharmacol. 4, 1307–1318. Lee, Y.J., Choi, B., Lee, E.H., Choi, K.S., Sohn, S., 2006. Immobilization stress induces cell death through production of reactive oxygen species in the mouse cerebral cortex. Neurosci. Lett. 392, 27–31. Madrigal, J.L., Moro, M.A., Lizasoain, I., Lorenzo, P., Fernandez, A.P., Rodrigo, J., Bosca, L., Leza, J.C., 2003. Induction of cyclooxygenase-2 accounts for restraint stress-induced oxidative status in rat brain. Neuropsychopharmacology 28, 1579–1588. Matsuwaki, T., Kayasuga, Y., Yamanouchi, K., Nishihara, M., 2006. Maintenance of gonadotropin secretion by glucocorticoids under stress conditions through the inhibition of prostaglandin synthesis in the brain. Endocrinology 147, 1087–1093. Matsuwaki, T., Suzuki, M., Yamanouchi, K., Nishihara, M., 2004. Glucocorticoid counteracts the suppressive effect of tumor necrosis factor-α on the surge of luteinizing hormone secretion in rats. J. Endocrinol. 181, 509–513. Matsuwaki, T., Watanabe, E., Suzuki, M., Yamanouchi, K., Nishihara, M., 2003. Glucocorticoid maintains pulsatile secretion of luteinizing hormone under infectious stress condition. Endocrinology 144, 3477–3482.
46
T. Matsuwaki et al. / Hormones and Behavior 54 (2008) 41–46
McGivern, R., Redei, E., 1994. Adrenalectomy reverses stress-induced suppression of luteinizing hormone secretion in long-term ovariectomized rats. Physiol. Behav. 55, 1147–1150. Mirescu, C., Gould, E., 2006. Stress and adult neurogenesis. Hippocampus 16, 233–238. Morale, M., Serra, P., Delogu, M., Migheli, R., Rocchitta, G., Tirolo, C., Caniglia, S., Testa, N., L'Episcopo, F., Gennuso, F., Scoto, G., Barden, N., Miele, E., Desole, M., Marchetti, B., 2003. Glucocorticoid receptor deficiency increases vulnerability of the nigrostriatal dopaminergic system: critical role of glial nitric oxide. FASEB J., 18, 164–166. Narita, K., Nishihara, M., Takahashi, M., 1994. Concomitant regulation of running activity and metabolic change by the ventromedial nucleus of the hypothalamus. Brain Res. 642, 290–296. Perry, J., Hipólide, D., Tufik, S., Martins, R., Da Cunha, C., Andreatini, R., Vital, M., 2005. Intra-nigral MPTP lesion in rats: behavioral and autoradiography studies. Exp. Neurol. 195, 322–329. Roozendaal, B., Nguyen, B.T., Power, A.E., McGaugh, J.L., 1999. Basolateral amygdala noradrenergic influence enables enhancement of memory consolidation induced by hippocampal glucocorticoid receptor activation. Proc. Natl. Acad. Sci. U. S. A. 96, 11642–11647. Saketos, M., Sharma, N., Santoro, N., 1993. Suppression of the hypothalamicpituitary-ovarian axis in normal women by glucocorticoids. Biol. Reprod. 49, 1270–1276.
Schmidt, W.J., Beninger, R.J., 2006. Behavioural sensitization in addiction, schizophrenia, Parkinson's disease and dyskinesia. Neurotox. Res. 10, 161–166. Shohami, E., Globus, M., Weidenfeld, J., 1985. Regional distribution of prostanoids in rat brain: effect of insulin and 2-deoxyglucose. Exp. Brain Res. 61, 87–90. Sloviter, R.S., Valiquette, G., Abrams, G.M., Ronk, E.C., Sollas, A.L., Paul, L.A., Neubort, S., 1989. Selective loss of hippocampal granule cells in the mature rat brain after adrenalectomy. Science 243, 535–538. Sudlow, A., Carey, F., Forder, R., Rothwell, N., 1996. The role of lipocortin-1 in dexamethasone-induced suppression of PGE2 and TNF alpha release from human peripheral blood mononuclear cells. Br. J. Pharmacol. 117, 1449–1456. Volpi, R., Caffarra, P., Marcato, A., Scaglioni, A., Maestri, D., Delsignore, R., Chiodera, P., Coiro, V., 1991. Reduced ACTH/cortisol responses to naloxone in men with Parkinson's disease. J. Neural. Transm., Parkinson's Dis. Dement. Sect. 3, 127–132. Volpi, R., Caffarra, P., Scaglioni, A., Saginario, A., Maestri, D., Vourna, S., Vescovi, P., Chiodera, P., Coiro, V., 1993. Lack of ACTH/cortisol and GH responses to intravenously-infused substance P in Parkinson's disease. J. Neural Transm., Parkinson's Dis. Dement. Sect. 6, 99–107. Yan, X.D., Kumar, B., Nahreini, P., Hanson, A.J., Prasad, J.E., Prasad, K.N., 2005. Prostaglandin-induced neurodegeneration is associated with increased levels of oxidative markers and reduced by a mixture of antioxidants. J. eurosci. Res. 81, 85–90.