Brain vasopressin is involved in stress-induced suppression of immune function in the rat

Brain Research 808 Ž1998. 84–92

Research report

Brain vasopressin is involved in stress-induced suppression of immune function in the rat Tamotsu Shibasaki

a,b,)

, Mari Hotta c , Hitoshi Sugihara b , Ichiji Wakabayashi

b

a

Department of Physiology, Nippon Medical School, 1-1-5 Sendagi, Bunkyo-ku, Tokyo 113-8602, Japan Department of Medicine, Nippon Medical School, 1-1-5 Sendagi, Bunkyo-ku, Tokyo 113-8602, Japan Department of Medicine, Institute of Clinical Endocrinology, Tokyo Women’s Medical UniÕersity, 8-1 Kawada-cho, Shinjuku-ku, Tokyo 162-8666, Japan b

c

Accepted 11 August 1998

Abstract The possibility that vasopressin ŽVP. is involved in stress-induced suppression of immune function was examined in rats. Intermittent electrical footshock for 60 min suppressed the proliferative response of splenic T cells to the mitogen concanavalin A as well as natural killer ŽNK. cytotoxicity, and the former change was partially, and the latter was completely, blocked by intracerebroventricular Ži.c.v.. preadministration of a V1 receptor antagonist. The footshock-induced suppression of the T cell proliferative response was completely abolished by coadministration of a corticotropin-releasing hormone ŽCRH. receptor antagonist and the V1 receptor antagonist. The i.c.v. administration of VP suppressed the proliferative response of splenic T cells and NK cytotoxicity in an adrenal-independent manner. These effects were completely reversed by i.c.v. preadministration of the V1 receptor antagonist. These results suggest that brain VP, in conjunction with CRH, suppresses immune function through the V1 receptor in rats under stress. q 1998 Elsevier Science B.V. All rights reserved. Keywords: Vasopressin; V1 receptor; T cell; NK cytotoxicity; Corticotropin-releasing hormone; Stress

1. Introduction Stress induces various changes in the neuroendocrine system, the autonomic nervous system, behavior, mood, and the immune system. Among these changes, brain corticotropin-releasing hormone ŽCRH. plays important roles to integrate changes in stress, such as stimulation of the pituitary–adrenal axis w32x, suppression of the pituitary–gonadal axis w33x, stimulation of epinephrine secretion from the adrenal medulla w6x, inhibition of gastric acid secretion w39x, stimulation of the transit time of the colon w44x, suppression of feeding behavior w25,35x, and increasing of arousal w37x and offensive mood w42x. In addition, recent studies have revealed that both intracerebroventricular Ži.c.v.. administration of CRH and stress inhibit immune function, such as splenic natural killer ŽNK. cytotoxicity, the proliferative response of T cell in peripheral blood to a mitogenic agent, and specific antibody production to a novel antigen, and that brain CRH is involved in

) Corresponding author. Department of Physiology, Nippon Medical School, 1-1-5 Sendagi, Bunkyo-ku, Tokyo 113-8602, Japan. Fax: q81-33822-0766

the mechanism of inhibition of the immune function by stress in rats w20–22x. The release of both vasopressin ŽVP. and CRH increases in response to stress, and VP as well as CRH participate in the mechanism of stimulation of the pituitary–adrenal axis in stress w32x. Besides the action on the pituitary–adrenal axis, evidence has accumulated suggesting the roles of VP in a variety of central nervous system functions, such as learning, memory, and the regulation of body temperature and cardiovascular system w13x. Further, VP is found to mediate emotional stress-induced colonic motor alterations, suggesting the involvement of central nervous system VP in various stress responses w7x. Therefore, the present study was designed to clarify whether brain VP is also involved in the stress-induced suppression of immune function in the rat. To this end, the effects of intracerebroventricular Ži.c.v.. administration of a VP V1 receptor antagonist on the electrical footshock-induced suppression of the splenic T cell proliferative response to concanavalin A Žcon A., a T cell mitogenic agent, and splenic NK cytotoxicity were tested. Furthermore, the effects of i.c.v. administration of VP on the proliferative response of splenic T cells to con A and on splenic NK activity were examined in rats.

0006-8993r98r$ - see front matter q 1998 Elsevier Science B.V. All rights reserved. PII: S 0 0 0 6 - 8 9 9 3 Ž 9 8 . 0 0 8 4 3 - 9

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2. Materials and methods

2.1. Animals Male Wistar rats weighing 180–200 g, individually housed under conditions of controlled temperature and illumination Ž0800–2000 h. and allowed ad libitum access to food and water, were used in this study. The right lateral ventricle Žrostral, 0.0 mm; lateral, 1.8 mm; ventral, 5.0 mm, relative to the bregma and the dural surface. of the animals was implanted with a polyethylene guide cannula Žlength, 7.5 mm; i.d., 0.58 mm; o.d., 0.96 mm; Natsume, Tokyo, Japan. under sodium pentobarbital anesthesia 5 days before the experiment, as reported previously w35–37x. On the same day, bilateral adrenalectomy or sham-adrenalectomy was performed in 24 rats. Those rats were allowed saline instead of water and were intraperitoneally administered 10 mg dexamethasone daily until 36 h before Expt. 4 described below. The dose of dexamethasone administered was determined according to a previous report w22x. On the day of experiment, an injection cannula Žlength, 15 cm; i.d., 0.28 mm; o.d., 0.61 mm; polyethylene tube, Natsume, Tokyo, Japan. connected to a 10 ml microsyringe was inserted into the guide cannula. Then, sample solution or vehicle was injected into the lateral ventricle through the cannula for 1 min. The injection cannula was left in place for an additional minute to prevent backflow of the solution.

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2.2. Experimental protocols 2.2.1. Experiment 1 Seventy-five nanograms of b-mercapto-b,b-cyclopentamethylene-propionic acid o-methyl-L-tyrosine arginine vasopressin, a V1 receptor antagonist ŽPeptide Institute, Osaka, Japan. dissolved in 0.9% saline, the same dose of the V1 receptor antagonist with 100 mg of a-helical CRH Ž9-41., a CRH receptor antagonist, dissolved in 0.1 N NH 4 HCO 3 , or vehicle as the control was administered i.c.v. to rats. The V1 receptor antagonist dose was determined according to a previous report w24x. The volume of sample injected i.c.v. was 9 ml. After 15 min, the rats were given electrical footshocks through grids with electric currents Ž1.5 mA, 1 s duration. delivered randomly on an average of twice per min for 60 min. 2.2.2. Experiment 2 VP Ž3 or 10 ng. dissolved in 2 ml of 0.9% saline or the same volume of vehicle as the control was administered i.c.v. to rats through the guide cannula. 2.2.3. Experiment 3 The V1 antagonist Ž75 ng. dissolved in 2 ml of 0.9% saline or the same volume of vehicle as the control was administered i.c.v. to rats. After 15 min, 10 ng of VP dissolved in 2 ml of 0.9% saline or vehicle was administered i.c.v. to the animals. 2.2.4. Experiment 4 VP Ž10 ng. dissolved in 2 ml of 0.9% saline or vehicle was administered i.c.v. to bilateral adrenalectomized rats.

Fig. 1. The effect of the VP receptor antagonist on the footshock-induced suppression of the proliferative response of T cells to concanavalin A Žcon A.. The i.c.v. administration of the VP receptor antagonist Ž75 ng. partially inhibited the footshock-induced suppression of the proliferative response of T cells to 2.5 mgrml con A.

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Fig. 2. The effect of the VP receptor antagonist on the footshock-induced suppression of NK cytotoxicity. The i.c.v. administration of the VP receptor antagonist Ž75 ng. reversed the footshock-induced suppression of NK cytotoxicity at an effectorrtarget cell ratio of 100:1.

2.3. Cell preparation The animals were decapitated 60 min after sample administration or after the 60 min period of intermittent footshock stress, and the spleens removed, as previously described w22x. Each spleen was minced and the tissue fragments then gently pressed using a plastic rod, the top of which is flat and round. After being filtered through a nylon mesh, the cells were suspended in phosphate-buffered

saline and centrifuged in 17 ml tubes at 400 = g at room temperature for 30 min over Ficoll-Paque ŽPharmacia Biotech, Uppsala, Sweden. to produce mononuclear cells. Cells at the interface were collected and washed twice with phosphate-buffered saline. The washed cells were suspended in RPMI1640 ŽLife Technologies, Paisley, Scotland. containing 5% fetal bovine serum ŽFBS. or Medium 199 ŽLife Technologies, Paisley, Scotland.. containing 10% FBS for the analysis of the T cell proliferative response to

Fig. 3. The effect of the VP receptor antagonist and the CRH receptor antagonist on the footshock-induced suppression of the proliferative response of T cells to con A. The i.c.v. coadministration of the VP receptor antagonist Ž75 ng. and the CRH receptor antagonist Ž100 mg. completely reversed the footshock-induced suppression of the proliferative response of T cells to con A.

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Fig. 4. The effect of VP on the proliferative response of splenic T cells to con A. The i.c.v. administration of VP significantly suppressed the proliferative response of T cells to con A at doses of 3 ng and 10 ng. The concentrations of con A were 0.625, 1.25, and 2.5 mgrml.

con A ŽSigma-Aldrich Japan, Tokyo, Japan. or of NK cytotoxicity, respectively. 2.4. T cell proliferation assay Splenic mononuclear cells suspended in RPMI1640 containing 5% FBS at a concentration of 1 = 10 6rml and kept in 96 well microtiter plates were used for the analysis of the T cell proliferative response to con A. Cells in 0.2 ml of medium were incubated in the presence of con A at final concentrations of 0.625, 1.25, or 2.50 mgrml for 48 h at 378C in 95% air and 5% CO 2 . 3 H-thimidine was then

added into the medium and the cells incubated for another 18 h. Cells were harvested onto filter paper using a multiple sample harvester and radioactivity incorporated into the cells was determined in a liquid scintillation counter. The proliferative response of T cells to con A was expressed as follows: stimulation index ŽS.I.. s experimental 3 Hrbasal 3 H. 2.5. Determination of NK cytotoxicity Mouse YAC-1 cells ŽDainippon Pharmaceutical, Oosaka, Japan. were labeled with 51 chromium Ž51 Cr. and

Fig. 5. The effect of VP on NK cytotoxicity. The i.c.v. administration of VP significantly suppressed NK cytotoxicity at an effectorrtarget cell ratio of 200:1 and effectorrtarget cell ratios of 50:1, 100:1, and 200:1 at VP doses of 3 ng and 10 ng, respectively.

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Fig. 6. The effect of the VP receptor antagonist on VP-induced suppression of the proliferative response of T cells to 2.5 mgrml con A. The VP receptor antagonist Ž75 ng., preadministered i.c.v., completely abolished the suppressive effect of VP Ž10 ng..

used as the target cells. Splenic cells prepared from the experimental rats and suspended in 100 ml of medium as described above and 51 Cr-labeled YAC-1 cells Ž1 = 10 4 in 40 ml. were cocultured in microtiter plates at 200:1 to 25:1 effector to target ratios for 4 h at 378C in 95% air and 5% CO 2 . Control wells were used to quantitate the total amount of 51 Cr that was incorporated by the target cells; 0.1 N HCl was added to target cells during the incubation, yielding the value for total release of 51 Cr. Additional control wells were used to evaluate the spontaneous release of 51 Cr into culture medium by incubating the target

cells in medium alone. The amount of 51 Cr in culture medium was then counted after centrifugation, and NK cell activity was determined as follows and as previously described w30x: % cytotoxicitys Žexperimental 51 Cr release y spontaneous 51 Cr release.rŽtotal 51 Cr release y spontaneous 51 Cr release. = 100. 2.6. Statistical analysis All data were expressed as the mean " S.E.M.. Data were subjected to analysis of variance, and group comparisons were performed using Scheffe’s F-test or Fisher’s

Fig. 7. The effect of the VP receptor antagonist on VP-induced suppression of NK cytotoxicity. The VP receptor antagonist Ž75 ng., preadministered i.c.v., completely abolished the suppressive effect of VP Ž10 ng. on NK cytotoxicity at an effectorrtarget cell ratio of 100:1.

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Fig. 8. The effect of adrenalectomy on VP-induced suppression of the proliferative response of T cells to con A. The i.c.v. administration of VP Ž10 ng. significantly suppressed the proliferative response of T cells to con A in both the adrenalectomized and sham-adrenalectomized rats.

protected least significance test. A p-value less than 0.05 was taken as the criterion for significance.

3. Results 3.1. Effects of V1 receptor antagonist and CRH receptor antagonist on footshock-induced suppression of immune function Intermittent electrical footshock for 60 min significantly suppressed the proliferative response of T cells to 0.625,

1.25 or 2.5 mgrml con A, and the suppression of the proliferative response of T cells to 2.5 mgrml con A was partially attenuated by the i.c.v. administration of 75 ng of the V1 receptor antagonist ŽFig. 1., while the suppression of NK cytotoxicity by intermittent electrical footshock for 60 min was completely blocked by the V1 receptor antagonist at an effectorrtarget cell ratio of 100:1 ŽFig. 2.. Therefore, 100 mg of a-helical CRH Ž9-41. was coadministered i.c.v. with the V1 receptor antagonist to rats before being exposed to footshock stress to test the possibility that CRH is also involved in the suppression of the proliferative response of T cells to con A. The suppression of

Fig. 9. The effect of adrenalectomy on VP-induced suppression of NK cytotoxicity. The i.c.v. administration of VP Ž10 ng. significantly suppressed NK cytotoxicity at an effectorrtarget cell ratio of 100:1 in both the adrenalectomized and sham-adrenalectomized rats.

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the proliferative response of T cells to 1.25 or 2.5 mgrml con A by 60 min electrical footshock was completely reversed by the i.c.v. coadministration of the V1 receptor antagonist Ž75 ng. and a-helical CRH Ž9-41. Ž100 mg. ŽFig. 3.. 3.2. Effects of VP and V1 receptor antagonist on immune function The i.c.v. administration of VP significantly inhibited the proliferative response of T cells to con A at doses of 3 and 10 ng ŽFig. 4.. The NK cytotoxicity was also significantly inhibited by the i.c.v. administration of 3 ng and 10 ng of VP at an effectorrtarget cell ratio of 200:1 and at effectorrtarget cell ratios of 50:1, 100:1, and 200:1, respectively ŽFig. 5.. The inhibitory effect of 10 ng VP on the proliferative response of T cells to 2.5 mgrml con A was completely blocked by i.c.v. preadministration of 75 ng of the V1 receptor antagonist, while the V1 receptor antagonist alone did not show any significant effect on the proliferative response of T cells to con A ŽFig. 6.. The inhibitory effect of 10 ng VP on NK cytotoxicity was also blocked by preadministration of 75 ng of the V1 receptor antagonist at an effectorrtarget cell ratio of 100:1, while the V1 receptor antagonist alone did not affect NK cytotoxicity ŽFig. 7.. 3.3. Effects of VP on immune function in adrenalectomized rats The i.c.v. administration of 10 ng of VP significantly suppressed the proliferative response of T cells to con A in both bilateral adrenalectomized and sham-adrenalectomized rats ŽFig. 8.. The inhibitory effect of 10 ng VP on NK cytotoxicity was also found at an effectorrtarget cell ratio of 100:1 in the adrenalectomized rats ŽFig. 9..

4. Discussion The present study demonstrated that footshock stress induces suppression of the proliferative response of T cells to the mitogen con A and NK cytotoxocity, as reported previously by other research groups w20,22x, and that the inhibition of the T cell proliferative response is partially, and that of NK cytotoxicity is completely, blocked by i.c.v. administration of a V1 receptor antagonist. In addition, we found that i.c.v. administration of VP suppresses the proliferative response of T cells to con A and NK cytotoxicity, and that this inhibitory effect is reversed by i.c.v. administration of the V1 receptor antagonist. These findings indicate that brain VP acts as an inhibitor of immune function through V1 receptor in acute stress. Although the footshock stress-induced inhibition of immune function was reversed by the V1 receptor antagonist, there was a divergence between the data assessed by the T

cell proliferative response and NK cytotoxicity. We considered that the T cell proliferative response was superior to NK cytotoxicity to detect a small change in the inhibition of immune function associated with VP or CRH, since the difference between the control groups and the VPtreated groups was greater in the T cell proliferative response than in NK cytotoxicity as shown in Figs. 4 and 5. The stress-induced inhibition of the T cell proliferative response was completely blocked by the coadministration of the V1 receptor antagonist and a CRH receptor antagonist. Thus, it is indicated that both brain VP and CRH appear to be involved in the mechanism by which acute stress suppresses immune function. Brain CRH plays an important role in connecting various stressors with stress responses w6,25,32,33,35,39,42,44x. Recent studies have revealed that brain CRH is involved in the mechanism by which footshock stress suppresses immune function w20,22x. However, the inhibition of immune cell functions is not reversed completely by a-helical CRH Ž9-41., suggesting that a factor other than CRH participates in the mechanism by which acute stress inhibits immune system function w22x. This finding is in accordance with the results of our study, which indicate that VP, as well as CRH, is involved in the mechanism of acute stress-induced suppression of immune function. VP carried by the axons of the magnocellular neurons of the supraoptic nucleus and the paraventricular nucleus and released into the circulation through the posterior lobe of the pituitary regulates water balance w8x. On the other hand, the release of VP into the peripheral circulation also increases in response to various stressors, such as insulininduced hypoglycemia w3x, electric footshock w9x, ether w15x, and manual restraint w18x. The origin of VP released in response to such stressors seems to be the paraventricular nucleus, since some of the VP-neurons in the nucleus send fibers to the external zone of the median eminence where their terminals contact the hypophyseal portal capillaries w1,38x. This released VP appears to play a role in stimulating the release of ACTH by VP’s own action on the pituitary and by potentiating the stimulatory effect of CRH on ACTH secretion w16x. In addition, VP is known to enhance learning and memory w11,12x, and is distributed in several brain regions thought to be involved in memory processes, such as the mediodorsal thalamic nucleus, the hippocampus and the neocortex w13x. Furthermore, VP is reported to mediate emotional stress-induced colonic motor alterations in rats w7x, indicating that brain VP acts as a neurotransmitter in response to stress. Our results provide new evidence that VP also acts as a neurotransmitter to suppress the immune function in stress. Several subtypes of the VP receptor, the V1a, V2 and V3 Žor V1b. receptors have been cloned w4,10,26,40x. V1a receptors are expressed in the vascular structures of the kidney and in the central nervous system, and are considered to mediate the pressor action of VP on the vessels w31x. V2 receptors are predominantly expressed in kidney,

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and mediate the antidiuretic action of VP in the renal collecting tubules and the medullary thick ascending limb of Henle’s loop w26,31x. V3 receptors are expressed in the pituitary corticotropes as well as in multiple brain regions and a number of peripheral tissues w10,27x. Since V1 receptors exist in the central nervous system w43,45x, in the present study, we examined whether the V1 receptor is involved in the mechanism by which footshock stress suppresses immune function. The V1 receptor antagonist used was shown to abolish the suppressive effect of VP administered i.c.v. on T cell and NK cell function, as well as to attenuate the suppressive effect of intermittent footshock stress on immune function. These findings indicate that the V1 receptor mediates the inhibitory action of central nervous system VP on immune function. CRH administered i.c.v. is known to stimulate the sympathetic nervous system w5x. Abolishment of the inhibitory action of CRH on immune function by chlorisondamine, a ganglionic blocking agent w19x, suggests that CRH activates the sympathetic nervous system center in the central nervous system and causes inhibition of immune cell function. Splenic lymphoid tissue is innervated by sympathetic neural fibers w28x, and lymphocytes are directly contacted by the fibers w14x. Furthermore, VP administered i.c.v. increases sympathetic outflow w23x. Therefore, VP most likely acts either directly or indirectly on the autonomic nervous system center through the V1 receptors in the brain, thus causing the inhibition of immune cell function. However, it is not clear at present where the neurons which synthesize VP and respond to footshock stress, and where the V1 receptors which participate in the inhibitory mechanism of immune function by acute stress, are located in the central nervous system. Immunohistochemical studies have revealed that VP neurons are widely distributed in the brain w8x. The caudal portion of the paraventricular nucleus contains VP neurons and gives rise to a descending projection which distributes fibers to the sympathetic intermediolateral cell column of the thoracolumbar spinal cord and the parasympathetic vagal complex, the major sources of preganglionic autonomic outflow w34,41x. It is likely that the neurons participating in the regulation of the autonomic nervous system are involved in the mechanism of inhibition of immune function in stress. Furthermore, the VP containing magnocellular neurons of the supraoptic nucleus communicate via axon collaterals with other neurons in the lateral hypothalamus w29x, and a certain proportion of the small neurons present within the suprachiasmatic nucleus contain VP and their fibers have been traced to the dorsomedial hypothalamic nucleus w17x. Because the hypothalamus is the autonomic nervous system center, such VP-neurons may also be involved in the regulatory mechanism of immune function in stress. The absolute number of T-lymphocyte subpopulations or NK cells was not counted in the present study. However, the central administration of CRH is reported to

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reduce NK activity in both peripheral blood and spleen without altering the number of T-lymphocyte subpopulations or NK cells w20x. Furthermore, statistically significant alterations in splenic weight, number of total lymphocytes, or percentage of T-helper, T-suppressor, or NK cells are not found in rats receiving footshock w20x. Further investigations are needed to clarify the immunological mechanisms underlying the suppression of T cell proliferative response and NK cytotoxicity by footshock. Glucocorticoids are known to suppress immune cell functions w2x, and the secretion of corticosterone is stimulated by stress. VP itself stimulates the secretion of adrenocorticotropic hormone ŽACTH., and also potentiates the stimulatory action of CRH on ACTH secretion by the pituitary corticotropes w16x. Although the amount of VP leaked from the cerebroventricle into the peripheral blood after i.c.v. injection has been reported to be insufficient to induce the biological effects of VP w23x, we examined the possibility that VP administered i.c.v. might leak into the peripheral blood and stimulate the secretion of ACTH, causing the secretion of corticosterone and subsequent suppression of immune function. The results of our study showed that the proliferative response of T cell to con A and NK cytotoxicity are not affected by bilateral adrenalectomy. Therefore, the action of VP is thought to be independent of the pituitary–adrenal axis. In conclusion, VP released in conjunction with CRH in response to acute stress inhibits immune cell functions via the V1 receptors probably by stimulating the sympathetic nervous system in a pituitary–adrenal independent manner.

Acknowledgements This study was supported in part by a grant from the Japan Private School Promotion Foundation and a grant for anorexia nervosa from the Japanese Ministry of Health and Welfare.

References w1x J.L. Antunes, P.W. Carmel, E.A. Zimmerman, Projections from the paraventricular nucleus to the zona externa of the median eminence of the rhesus monkey: an immunohistochemical study, Brain Res. 137 Ž1977. 1–10. w2x A. Bateman, A. Singh, T. Kral, S. Solomon, The immune-hypothalamic–pituitary–adrenal axis, Endocr. Rev. 10 Ž1989. 92–112. w3x P.H. Baylis, G.L. Robertson, Rat vasopressin response to insulin-induced hypoglycemia, Endocrinology 107 Ž1980. 1975–1979. w4x M. Birnbaumer, A. Seibold, S. Gilbert, M. Ishida, C. Barberis, A. Antaramian, P. Brabet, W. Rosenthal, Molecular cloning of the receptor for human antidiuretic hormone, Nature 357 Ž1992. 333– 335. w5x M.R. Brown, L.A. Fisher, J. Spiess, C. Rivier, J. Rivier, W. Wale, Corticotropin-releasing factor: actions on the sympathetic nervous system and metabolism, Endocrinology 111 Ž1982. 928–931. w6x M. Brown, L.A. Fisher, V. Webb, W.W. Vale, J.E. Rivier, Corti-

92

w7x

w8x

w9x

w10x

w11x w12x

w13x w14x

w15x

w16x

w17x

w18x

w19x

w20x

w21x

w22x

w23x

w24x

w25x

w26x

w27x

T. Shibasaki et al.r Brain Research 808 (1998) 84–92 cotropin-releasing factor: a physiologic regulator of adrenal epinephrine secretion, Brain Res. 328 Ž1985. 355–357. L. Bueno, M. Gue, C. Delrio, CNS vasopressin mediates emotional stress and CRH-induced colonic motor alterations in rats, Am. J. Physiol. 262 Ž1992. G427–G431. R.M. Buijis, G.J. de Vries, F.W. van Leeuwen, D.F. Swaab, Vasopressin and oxytocin: distribution and putative functions in the brain, Prog. Brain Res. 60 Ž1983. 115–122. A.F. Crine, R.M. Buijs, Electric footshocks differentially affect plasma and spinal cord vasopressin and oxytocin levels, Peptides 8 Ž1987. 243–246. Y. De Keyzer, C. Auzan, F. Lenne, C. Beldjord, M. Thibonnier, X. Bertagna, E. Clauser, Cloning and characterization of the human V3 pituitary vasopressin receptor, FEBS Lett. 356 Ž1994. 215–220. D. De Wied, Long term effect of vasopressin on the maintenance of a conditioned avoidance response in rats, Nature 232 Ž1971. 58–60. D. De Wied, B. Bohus, T.B. Van Wimersma Greidanus, Memory deficit in rats with hereditary diabetes insipidus, Brain Res. 85 Ž1975. 152–156. P.A. Doris, Vasopressin and central integrative processes, Neuroendocrinology 38 Ž1984. 75–85. D.L. Felten, K.D. Ackerman, S.J. Wiegand, S.Y. Felten, Noradrenergic sympathetic innervation of the spleen: I. Nerve fibers associate with lymphocytes and macrophages in specific compartments of the splenic white pulp, J. Neurosci. Res. 18 Ž1987. 28–36. D.M. Gibbs, Dissociation of oxytocin, vasopressin and corticotropin secretion during different types of stress, Life Sci. 35 Ž1984. 487– 491. G.E. Gillies, E.A. Linton, P.J. Lowry, Corticotropin releasing activity of the new CRF is potentiated several times by vasopressin, Nature 299 Ž1982. 355–357. E.M.D. Hoorneman, R.M. Buijs, Vasopressin fiber pathways in the rat brain following suprachiasmatic nucleus lesioning, Brain Res. 243 Ž1982. 235–241. M.K. Husain, W.M. Manger, T.W. Rock, R.J. Weiss, A.G. Frantz, Vasopressin release due to manual restraint in the rat: role of body compression and comparison with other stress stimuli, Endocrinology 104 Ž1979. 641–644. M. Irwin, R.L. Hauger, M. Brown, K.T. Britton, CRF activates autonomic nervous system and reduces natural killer cytotoxicity, Am. J. Physiol. 24 Ž1988. R744–R747. M. Irwin, W. Vale, C. Rivier, Central corticotropin-releasing factor mediates the suppressive effect of stress on natural killer cytotoxicity, Endocrinology 126 Ž1990. 2837–2844. M. Irwin, Brain corticotropin-releasing hormone- and interleukin1b-induced suppression of specific antibody production, Endocrinology 133 Ž1993. 1352–1360. R. Jain, D. Zwickler, C.S. Hollander, H. Brand, A. Saperstein, B. Hutchinson, C. Brown, T. Audhya, Corticotropin-releasing factor modulates the immune response to stress in the rat, Endocrinology 128 Ž1991. 1329–1336. P. Janiak, B.G. Kasson, M.J. Brody, Central vasopressin raises arterial pressure by sympathetic activation and vasopressin release, Hypertension 13 Ž1989. 935–940. J.V. Johnson, G.W. Bennett, R. Hatton, Central and systemic effects of a vasopressin V1 antagonist on MAP recovery after haemorrhage in rats, J. Cardiovasc. Pharmacol. 12 Ž1988. 405–412. D.D. Krahn, B.A. Gosnell, M. Grace, A.S. Levine, CRF antagonist partially reverses CRF- and stress-induced effects on feeding, Brain Res. Bull. 17 Ž1986. 285–289. S.J. Lolait, A.M. O’Carroll, O.W. McBride, M. Konig, A. Morel, M.J. Brownstein, Cloning and characterization of a vasopressin V2 receptor and possible link to nephrogenic diabetes insipidus, Nature 357 Ž1992. 336–339. S.J. Lolait, A.M. O’Carroll, L.C. Mahan, C.C. Felder, D.C. Button,

w28x

w29x

w30x

w31x

w32x

w33x

w34x

w35x

w36x

w37x

w38x

w39x

w40x

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w43x

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W.S. Young III, E. Mezey, M.J. Brwonstein, Extrapituitary expression of the V1b vasopressin receptor gene, Proc. Natl. Acad. Sci. USA 92 Ž1995. 6783–6787. S. Livnat, S.Y. Felten, S.L. Carlson, D.L. Bellinger, D.L. Felten, Involvement of peripheral and central catecholamine systems in neural-immune interactions, J. Neuroimmunol. 10 Ž1985. 5–30. W.D. Mason, Y.W. Ho, G.I. Hatton, Axon collaterals of supraoptic neurons: anatomical and electrophysiological evidence for their existence in the lateral hypothalamus, Neuroscience 11 Ž1984. 169–182. P.M. Mathews, C.J. Froelich, W.L. Sibbitt Jr., A.D. Bankhurst, Enhancement of natural cytotoxicity by b-endorphin, J. Immunol. 130 Ž1983. 1658–1662. F. Park, D.L. Mattson, M.M. Skelton, A.W. Cowley Jr., Localization of the vasopressin V1a and V2 receptors within the renal cortical and medullary circulation, Am. J. Physiol. 273 Ž1997. R243–R251. C. Rivier, J.E. Rivier, W.W. Vale, Inhibition of adrenocorticotropic hormone secretion in the rat by immunoneutralization of corticotropin-releasing factor, Science 218 Ž1982. 377–379. C. Rivier, J. Rivier, W. Vale, Stress-induced inhibition of reproductive functions: role of endogeneous corticotropin-releasing factor, Science 231 Ž1986. 607–609. P.E. Sawchenko, L.W. Swanson, Immunohistochemical identification of neurons in the paraventricular nucleus of the hypothalamus that project to the medulla or to the spinal cord in the rat, J. Comp. Neurol. 205 Ž1982. 260–272. T. Shibasaki, N. Yamauchi, Y. Kato, A. Masuda, T. Imaki, M. Hotta, H. Demura, H. Oono, N. Ling, K. Shizume, Involvement of corticotropin-releasing factor in restraint-induced anorexia and reversion of the anorexia by somatostatin, Life Sci. 43 Ž1988. 1103–1110. T. Shibasaki, N. Yamauchi, M. Hotta, A. Masuda, H. Oono, I. Wakabayashi, N. Ling, H. Demura, Brain corticotropin-releasing factor acts as inhibitor of stress-induced gastric erosion in rats, Life Sci. 47 Ž1990. 925–932. T. Shibasaki, N. Yamauchi, M. Hotta, T. Imaki, T. Oda, N. Ling, H. Demura, Brain corticotropin-releasing hormone increases arousal in stress, Brain Res. 554 Ž1991. 352–354. M.V. Sofroniew, A. Weindl, I. Schinko, R. Wetzstein, The distribution of vasopressin-, oxytocin-, and neurophysin-producing neurons in the Guinea pig brain, Cell. Tissue Res. 196 Ž1979. 367–384. R.L. Stephens Jr., H. Yang, J.E. Rivier, Y. Tache, Intracisternal injection of CRF antagonist blocks surgical stress-induced inhibition of gastric secretion in the rat, Peptides 9 Ž1988. 1067–1070. T. Sugimoto, M. Saito, S. Mochizuki, Y. Watanabe, S. Hashimoto, H. Kawashima, Molecular cloning and functional expression of a cDNA encoding the human V1b vasopressin receptor, J. Biol. Chem. 269 Ž1994. 27088–27092. L.W. Swanson, H.G.J.M. Kuypers, The paraventricular nucleus of the hypothalamus; cytoarchitectonic subdivisions and the organization of projections to the pituitary, dorsal vagal complex and spinal cord as demonstrated by retrograde fluorescence double-labeling methods, J. Comp. Neurol. 194 Ž1980. 555–570. A. Tazi, R. Dantzer, M. Le Moal, J. Rivier, W.W. Vale, G.F. Koob, Corticotropin-releasing factor antagonist blocks stress-induced fighting in rats, Regul. Peptides 18 Ž1987. 37–42. J.J. Watters, C.W. Wilkinson, D.M. Dorsa, Glucocorticoid regulation of vasopressin V1a receptors in rat forebrain, Mol. Brain Res. 38 Ž1996. 276–284. C.L. Williams, J.M. Peterson, R.G. Villar, T.F. Burks, Corticotropin-releasing factor directly mediates colonic responses to stress, Am. J. Physiol. 253 Ž1987. G582–G586. R.S. Yamazaki, Q. Chen, S.S. Schreiber, R.D. Brinton, Localization of V1a vasopressin receptor mRNA expression in cultured neurons, astroglia, and oligodendroglia of rat cerebral cortex, Mol. Brain Res. 45 Ž1997. 138–140.