摘要:

The effects of the prostaglandin (PG) synthetase inhibitor indomethacin (IM) on basal and stress-induced activity of the hypothalamo-hypophyseal-adrenal (HHA) axis were investigated. IM was systemically administered to adult male rats in a single injection (5 mg/100 g BW s.c). The animals were sacrificed 24 h later, either under basal conditions, or following 30 min exposure to environmental temperature of 36°C. Serum ACTH and corticosterone (CS) were determined by RIA and CBG, respectively, and hypothalamic and adenohypophyseal PGE2 and total PGE concentrations were estimated by RIA. IM treatment resulted in elevated basal levels of both hormones. Heat exposure led to elevated serum ACTH and CS concentrations in both vehicle- and IM-treated groups, with the ACTH heat response in IM-treated animals being greater than that observed in controls. PGE2, and PGE1 plus PGE2 concentrations were markedly reduced in both hypothalamic and adenohypophyseal tissues, following IM treatment. This study demonstrates that simultaneous reductions in hypothalamic and adenohypophyseal PG concentrations are compatible with hyperactivity of the HHA axis

ISSN:0028-3835    

DOI:10.1159/000123054

出版商:S. Karger AG    

年代:1980

数据来源: Karger

摘要:

The present study was undertaken to evaluate the 24-hour periodicity in serum prolactin levels subsequent to transecting the ascending serotonergic system or ablating the suprachiasmatic nuclei (SCN) of adult (185 g) female rats. The ascending serotonergic system was transected at the level of the rostral mesencephalon using a 1.5 mm wide knife and the SCN was ablated with a modified Halász-Pupp knife. The effect of raphe transection (RT) or SCN ablation on the circadian rhythm in nonstress serum prolactin levels was assessed 45 days after surgery by measuring with radioimmunoassay the serum prolactin concentration in serial blood samples obtained from the tail vein of lightly restrained rats. Serum prolactin concentration in control and RT animals showed circadian periodicity; peak levels occurred during the midafternoon, 4 h prior to the dark phase of the lighting regime (lights on at 4 a.m., off at 6 p.m.). The amplitude of the fluctuations of both groups varied markedly and were related to the estrous cycle. However, RT animals showed a reduced amplitude in the rhythm. In controls peak prolactin levels on days of proestrus and estrus were 15–20 times higher than on days of diestrus. In contrast, serum prolactin levels in SCN-ablated rats did not vary with a circadian periodicity but rather showed random, low amplitude fluctuations. Reproductive cyclicity was also abolished by SCN ablation, i.e., SCN-ablated rats presented persistent vaginal cornification. These data indicate that circadian periodicity in serum prolactin levels is not compromised by sectioning the ascending serotonergic fibers but is abolished after ablating the S

ISSN:0028-3835    

DOI:10.1159/000123055

出版商:S. Karger AG    

年代:1980

数据来源: Karger

摘要:

Administration of the bovine pineal peptide threonylseryllysine (TSL) to unilaterally ovariectomized (UO) mice as a single intraperitoneal injection on the day of UO reduced the 5-day compensatory ovarian hypertrophy. The same dose of TSL (175 ng/animal) significantly (p < 0.01) reduced serum follicle stimulating hormone (FSH) in UO mice 24 h after surgery and administration of the peptide. In other experiments, adult male rats were anesthetized with urethane and given an intravenous injection of luteinizing hormone releasing hormone (LRH) followed by TSL in doses ranging from 1.5 to 1,500 ng/animal. TSL significantly delayed (p < 0.05) the 15- and 30-min surge of serum FSH observed in control animals after 120 or 180 min in 3 of the 4 doses used (1.5, 15 and 1,500 ng/animal). In the animals receiving 150 ng TSL the LRH-induced FSH surge was delayed (p < 0.05) until 30 min. The results indicate that the pineal tripeptide may inhibit or modify FSH secretion in the mouse and rat.

ISSN:0028-3835    

DOI:10.1159/000123056

出版商:S. Karger AG    

年代:1980

数据来源: Karger

摘要:

(± )pChloroamphetamine hydrochloride, at doses of 1–8 mg/kg i.p. in rats, caused a dose-related increase in serum corticosterone concentration. The increase occurred rapidly, within 30 min, and was over within 4 h. Evidence that the increase was mediated by serotonin release consisted of the following findings: (1) a similar increase did not occur with (±)o-chloroamphetamine or (±)p-chloro-α-methylbenzylamine, analogs of p-chloroamphetamine lacking its ability to deplete serotonin; (2) the increase was prevented by prior treatment with p-chlorophenylalanine, which reduced the brain stores of serotonin available for release by p-chloroamphetamine; (3) the increase was prevented by prior treatment with fluoxetine, an inhibitor of the uptake pump on serotonin neurons, which blocks serotonin release by p-chloroamphetamine, and (4) the increase was mimicked by fenfluramine and norfenfluramine, agents known to release brain serotonin in a manner similar to the action of p-chloroamphetamine. These findings strengthen earlier evidence that brain serotonin neurons have a stimulatory influence on pituitary-adrenocortical function in

ISSN:0028-3835    

DOI:10.1159/000123057

出版商:S. Karger AG    

年代:1980

数据来源: Karger

摘要:

Serum and adrenal corticosterone was measured by competitive protein-binding radioassay in rats subjected to saline injection, ACTH administration or ether fumes. Groups of rats were tested at 5, 7, 9, 11, 13, 15, 20 and 25 days of age and measurement of hormone level was made either before treatment, to obtain basal values, or 15 min after treatment. Furthermore, the time-course of corticosterone release after ether was determined in 9- and 15-day-old rats. Neonatal rats responded to ether exposure, ACTH administration or saline injection with a significant rise in serum and adrenal corticosterone concentration above basal levels as early as 5 days of age. By 9 days of age, response to stress was qualitatively the same as that of the 25-day-old rat. The time course of adrenal responsiveness to ether stress was similar in 9- and 15-day-old rats, both age groups showing significant increases in hormone concentration by 15 min. These results contradict the concept of the ‘stress non-responsive period’ which was promoted by previous studies based on the nuorometric analysis of corticoster

ISSN:0028-3835    

DOI:10.1159/000123058

出版商:S. Karger AG    

年代:1980

数据来源: Karger

摘要:

Melatonin was slowly and intermittently infused into rats via an apparatus that allowed it to be discharged from a subcutaneous implant according to a predetermined temporal program. We found that infusion of an aqueous solution of melatonin, mixed with a dye, or of an immiscible fluid lacking melatonin or dye, could be monitored by measuring levels of melatonin or of dye in the rats’ urine. We observed a 24-hour rhythm in melatonin excretion which corresponded to the times of its infusion by the apparatus. Approximately 0.1% of infused melatonin was recovered unchanged in the urine. This method of administering exogenous melatonin may facilitate explaining the physiological significance of rhythms in its secretion and rhythms in plasma levels of other hormone

ISSN:0028-3835    

DOI:10.1159/000123059

出版商:S. Karger AG    

年代:1980

数据来源: Karger

摘要:

The concentration of dopamine (DA) and the accumulation of DOPA following the administration of a decarboxylase inhibitor were determined in the rat striatum, median eminence and posterior pituitary, regions containing terminals of nigrostriatal, tuberoinfundibular and tuberohypophyseal DA nerves, respectively. Severe dehydration (2 days water deprivation followed by 3 days of 2% NaCI substituted for drinking water) incressed the concentration of DA in the posterior pituitary but not in the striatum or median eminence. Less severe dehydration caused by 2 or 3 days of water deprivation did not alter steady state concentrations of DA, but increased DOPA accumulation, an index of DA nerve activity, only in the posterior pituitary. Food deprivation for 3 days did not alter DOPA accumulation in the posterior pituitary. These results suggest that dehydration selectively activates the tuberohypophyseal DA neuronal system in the rat.

ISSN:0028-3835    

DOI:10.1159/000123060

出版商:S. Karger AG    

年代:1980

数据来源: Karger

摘要:

The effects of MSH on spontaneous and induced ovulation as well as on serum LH levels were studied. Rats which received progesterone on D1 and D3 were injected i.p. with 30 μg of α-MSH or saline solution and examined for ovulation on the following day. The injection of α-MSH induced ovulation in 90% of the animals; saline solution, on the contrary, induced an ovulatory response only in 10% of the cases. Rats injected with β-MSH yielded similar results to those injected with saline solution, indicating a possible specific α-MSH action. The replacement of the second progesterone injection by α-MSH failed to increase ovulation indicating that α-MSH synergizes or alters progesterone action. It would seem that α-MSH stimulates ovulation-potentiating progesterone effects on the CNS. LH effectively induced ovulation in rats where spontaneous ovulation was blocked by an injection of progesterone on D1. The i.p. injection of 30 μg α-MSH lowered the amount of LH necessary to induce ovulation. Rats which received α-MSH and LRH showed a marked increase in serum LH levels compared with rats where α-MSH had been replaced by saline solution. Collectively the information provided in this paper is consistent with the view that the release of MSH observed in the morning of PE would signal the discharge of LH from the pituitary gland occurring in the afte

ISSN:0028-3835    

DOI:10.1159/000123061

出版商:S. Karger AG    

年代:1980

数据来源: Karger

摘要:

To further define the sites in the brain at which clonidine acts to lower blood pressure, inhibit renin secretion, inhibit ACTH secretion, and stimulate growth hormone secretion, small doses of this drug were infused into the vertebral arteries, into the carotid arteries and intravenously in pentobarbital-anesthetized dogs. Because injections of radioactive microspheres demonstrated that vertebral blood reached the hypothalamus, intravertebral and intracarotid infusions were also carried out after occlusion of the basilar artery in the midpontine region. Intracarotid clonidine, 2 μg/kg, decreased plasma ACTH and corticoids and increased plasma growth hormone, whereas the same dose had no effect on these hormones when given intravenously or when given intravertebrally after occlusion of the basilar artery. Intravertebral clonidine lowered blood pressure to a greater degree than intracarotid and intravenous clonidine. The reduction in heart rate produced by clonidine was essentially the same whether the drug was administered via the intravenous, intracarotid, or intravei tebral route. Intracarotid and intravertebral clonidine decreased plasma renin activity whereas in this dose intravenous clonidine did not. However, there was no renin response to intracarotid and intravertebral clonidine when the basilar artery was occluded. The data support the conclusion that clonidine acts rostral to the pons to decrease ACTH secretion and increase growth hormone secretion, whereas it acts on the medulla or adjacent hindbrain to lower blood pressure. In the dose used, clonidine appears to affect heart rate by a peripheral rather than a central action. The data confirm the observation that clonidine acts on the brain to inhibit renin secretion, and establish that the renin-inhibiting site is different from the blood pressure-lowering site. However, they do not permit localization of the renin-lowering site within the brain

ISSN:0028-3835    

DOI:10.1159/000123062

出版商:S. Karger AG    

年代:1980

数据来源: Karger

摘要:

Melatonin administered to female hamsters kept under light:dark cycles of 14:10 (in hours) normally suppresses reproductive processes only if the indoleamine is administered later than 6.5 h after the beginning of the photoperiod. In the present study, we investigated the influence of morning (11.00h) injections of melatonin on the reproductive inhibitory effects of afternoon (17.00 h) melatonin injections. Adult female hamsters were exposed to light daily from 06.00 to 20.00 h. The animals were divided into the following experimental groups: group 1, injected with vehicle at both 11.00 and 17.00 h; group 2, injected with vehicle at 11.00 h and 25 μg melatonin at 17.00 h; group 3, injected with 1 mg melatonin at 11.00 h and 25 μg melatonin at 17.00 h; group 4, injected with 1 mg melatonin at 11.00 h and vehicle at 17.00 h. Control animals injected with vehicle at both 11.00 and 17.00 h had normal 4-day estrous cycles throughout the 8 weeks of the experiment. 100% of the animals injected with vehicle in the morning and melatonin in the afternoon became acyclic within 7 weeks. However, if the afternoon injections of melatonin were preceded by morning injections of the indoleamine, the animals continued to exhibit normal estrous cycles. Also, hamsters injected with melatonin at 11.00 h and vehicle at 15.00 h had normal estrous cycles throughout the study. At the conclusion of the experiment, the uterine weights and plasma prolactin levels in the animals that received vehicle at 11.00 h and melatonin at 17.00 h were depressed compared to those in the vehicle-vehicle injected controls. Again, the morning injections of melatonin prevented the afternoon injections of melatonin from decreasing either the uterine weights or the plasma prolactin levels. It is concluded that the morning injections of melatonin either down-regulated the melatonin receptors or decreased their number and thereby rendered afternoon injections of melatonin incapable of inhibiting reproductive processe

ISSN:0028-3835    

DOI:10.1159/000123063

出版商:S. Karger AG    

年代:1980

数据来源: Karger