- Email: [email protected]
2324 Effects of adrenoceptor antagonists on neuroendocrine responses to conditioned fear stimuli in rats
S273
2324 Department
EFFECTS OF ADRENOCEPTOR ANTAGONISTS ON NEUROENDOCRINE SPONSES TO CONDITIONED FEAR STIMULI IN RATS of Physiology, Jichi Medical School, Minamikawachi-machi, Tochigi-ken. Japan 329-04
CHANG-JIANG
ZOU, TATSUSHI
ONAKA,
RE-
KINJI YAGI
Conditioned fear stimuli suppress vasopressin (VP) and facilitate oxytocin (OT) secretion by the pituitary. In the previous experiment, depletion of central noradrenaline blocked the neuroendocrine responses to fear stimuli. The present study aimed to identify the adrenoceptor subtypes which are involved in these responses. Male Wistar rats were trained with environmental stimuli paired with footshocks and tested with the environmental stimuli on the following day. Immediately after the testing, blood samples were collected. Adrenoceptor antagonists were injected i.c.v. 30min before the testing. In the rats that received benoxathian, an oi-receptor antagonist, the VP and OT responses to conditioned fear stimuli disappeared. Metoprolol, a ,3i-receptor antagonist, selectively blocked the VP response but not the OT response to conditioned fear stimuli. ICI 118551, a &receptor antagonist, did not significantly change the VP and OT responses to conditioned fear stimuli. We conclude that oi-receptors are involved in the VP and OT responses and that Pi-receptors are selectively associated with the VP response to conditioned fear stimuli in
2325
EFFECTS OF SEX STEROID HORMONE ON SEROTONIN-IMMUNOREACTIVITY IN THE FEMALE RAT BRAIN Department of Anatomy and Neurobiology, Kyoto Prefectural University of Medicine, KawaramachiHirokoji, Kyoto 602, Japan HAIPING LU, KAZUNARI YURI, MITSUHIRO KAWATA It is indicated that the sex steroid hormone regulate the secretion of serotonin, since it is demonstrated that serotonin serves an inhibitory role in the sexual behavior of the female rats, and this effect is decreased by sex steroid hormone treatment. In this ‘study, we investigated the serotonin-immunoreactivity in various parts of brain, including the area involved sexual behavior in ovariectomized (OVX) rats and OVX-rats treated with sex steroid hormone by using immunohistochemistry. It is noted that there is tendency to decrease in the density of serotonin-immunoreactive fibers in OVX-rat treated with sex steroid hormone, although the distribution of serotonin immunoreactive fibers did not change between OVX rats and OVX with sex steroid hormone.
2326
Stimulatory effects of glucose on the attenuation of the GnRH pulse generator by insulininduced hypoglycemia in the estrogen-primed ovariectomized rat
Dept. Physiol. Yokohama city Univ.‘,
Dept. Gynecol. 2
KINTOK KA’, TOSHIYA FUNABASHI’, TSUGUO UEMURA2, KOUJI MINAKUCH12, FUKUKO KIMURAl We investigated the effect of glucose on the attenuation of the electrical activity of GnRH pulse generator by insulin-induced hypoglycemia with or without estrogen priming. Injection of insulin (l-lOUnit/kg iv) suppressed the GnRH pulse generator in the estrogen-primed ovariectomized (OVX) rat but not in the OVX rat. This effect was immediately reversed by injection of glucose but not fructose. Also, opioid antagonist naloxone did not reverse the effect of insulin. The result indicates that the attenuation of the activity of GnRH pulse generator by insulin-induced hypoglycemia is dependent on estrogen-priming. Further, opioid neurons are not involved in attenuation of the GnRH pulse generator activity. Since estrogen rapidly enhances the inhibitory effect of hypoglycemia on the GnRH pulse generator activity, we speculate that there may be a cross talk between estrogen and glucose.
2324 Department
EFFECTS OF ADRENOCEPTOR ANTAGONISTS ON NEUROENDOCRINE SPONSES TO CONDITIONED FEAR STIMULI IN RATS of Physiology, Jichi Medical School, Minamikawachi-machi, Tochigi-ken. Japan 329-04
CHANG-JIANG
ZOU, TATSUSHI
ONAKA,
RE-
KINJI YAGI
Conditioned fear stimuli suppress vasopressin (VP) and facilitate oxytocin (OT) secretion by the pituitary. In the previous experiment, depletion of central noradrenaline blocked the neuroendocrine responses to fear stimuli. The present study aimed to identify the adrenoceptor subtypes which are involved in these responses. Male Wistar rats were trained with environmental stimuli paired with footshocks and tested with the environmental stimuli on the following day. Immediately after the testing, blood samples were collected. Adrenoceptor antagonists were injected i.c.v. 30min before the testing. In the rats that received benoxathian, an oi-receptor antagonist, the VP and OT responses to conditioned fear stimuli disappeared. Metoprolol, a ,3i-receptor antagonist, selectively blocked the VP response but not the OT response to conditioned fear stimuli. ICI 118551, a &receptor antagonist, did not significantly change the VP and OT responses to conditioned fear stimuli. We conclude that oi-receptors are involved in the VP and OT responses and that Pi-receptors are selectively associated with the VP response to conditioned fear stimuli in
2325
EFFECTS OF SEX STEROID HORMONE ON SEROTONIN-IMMUNOREACTIVITY IN THE FEMALE RAT BRAIN Department of Anatomy and Neurobiology, Kyoto Prefectural University of Medicine, KawaramachiHirokoji, Kyoto 602, Japan HAIPING LU, KAZUNARI YURI, MITSUHIRO KAWATA It is indicated that the sex steroid hormone regulate the secretion of serotonin, since it is demonstrated that serotonin serves an inhibitory role in the sexual behavior of the female rats, and this effect is decreased by sex steroid hormone treatment. In this ‘study, we investigated the serotonin-immunoreactivity in various parts of brain, including the area involved sexual behavior in ovariectomized (OVX) rats and OVX-rats treated with sex steroid hormone by using immunohistochemistry. It is noted that there is tendency to decrease in the density of serotonin-immunoreactive fibers in OVX-rat treated with sex steroid hormone, although the distribution of serotonin immunoreactive fibers did not change between OVX rats and OVX with sex steroid hormone.
2326
Stimulatory effects of glucose on the attenuation of the GnRH pulse generator by insulininduced hypoglycemia in the estrogen-primed ovariectomized rat
Dept. Physiol. Yokohama city Univ.‘,
Dept. Gynecol. 2
KINTOK KA’, TOSHIYA FUNABASHI’, TSUGUO UEMURA2, KOUJI MINAKUCH12, FUKUKO KIMURAl We investigated the effect of glucose on the attenuation of the electrical activity of GnRH pulse generator by insulin-induced hypoglycemia with or without estrogen priming. Injection of insulin (l-lOUnit/kg iv) suppressed the GnRH pulse generator in the estrogen-primed ovariectomized (OVX) rat but not in the OVX rat. This effect was immediately reversed by injection of glucose but not fructose. Also, opioid antagonist naloxone did not reverse the effect of insulin. The result indicates that the attenuation of the activity of GnRH pulse generator by insulin-induced hypoglycemia is dependent on estrogen-priming. Further, opioid neurons are not involved in attenuation of the GnRH pulse generator activity. Since estrogen rapidly enhances the inhibitory effect of hypoglycemia on the GnRH pulse generator activity, we speculate that there may be a cross talk between estrogen and glucose.