摘要:

In the rat exposed to constant light, mating reliablyproduces a rapid rise in plasma LH, leading to ovulation. To obtain information on the hypothalamo-pituitary mechanisms involved, changes in LHRF activity of the hypothalamus were studied following mating, and the sensitivity of the pituitary to LHRF was compared in rats exposed to constant light and normally cycling rats. Acid extracts of the medial basal hypothalamus were injected into spayed estrogen-progesterone-treated recipients and the response measured was radioimmunoassayable plasma LH. A decline in LHRF activity of the basal hypothalamus was observed which reached a low point at 20 min after the onset of mating, followed by a return toward the initial level, suggesting rapid release of stored LHRF followed by re-synthesis. No evidence was obtained for altered sensitivity of the pituitary to synthetic LHRF in rats exposed to constant light, in terms of plasma LH response. It was concluded that the particular sensitivity of the rat exposed to constant light to ovulation-inducing stimuli does not result from a high sensitivity of the pituitary to LHRF.

ISSN:0028-3835    

DOI:10.1159/000122253

出版商:S. Karger AG    

年代:1974

数据来源: Karger

摘要:

The effects of selective degeneration of brainserotoninergic nerve terminals by 5,6-dihydroxytryptamine (5,6-DHT) injected intraventricularly in prepuberal male rats were studied in 2 experiments. In both experiments, male Sprague-Dawley rats were injected in a lateral ventricle of the brain at 21 and 23 days of age with either 5,6-DHT or vehicle, and autopsied 1,2 and 4 weeks after the 1st injection. Controls were either pair-fed or fed ad lib. In the first experiment the effects of 5,6-DHT on body and organ growth and pituitary levels of radioimmunoassayable growth hormone (GH) were studied. In the second experiment the effects of 5,6-DHT on plasma and pituitary levels of radioimmunoassayable follicle-stimulating hormone (FSH) were studied. Histological examinations of the testes obtained at 4 weeks were performed. Experimental animals on the whole ate 41.8 % less food than controls fed ad lib. The analysis of variance showed that experimental animals, when compared with pair-fed controls, had significantly lower brain 5-HT levels (as measured by spectrophotofluoro-metry) at 1 and 2 weeks, significantly lower body weights at 1 week, and significantly smaller tails at 1 and 2 weeks after the first injection. Brain weights of experimental rats were significantly lower than those of controls fed ad lib. at 2 and 4 weeks; those of pair-fed animals, although lower at 2 weeks, were not significantly different from brain weights of controls fed ad lib. at 4 weeks. At 4 weeks, testes weights (corrected for body weights) were significantly lower in experimental rats than in controls fed ad lib. At 2 weeks, both the experimental and the pair-fed group had pituitary GH levels (corrected for body weights) lower than those of the group fed ad lib. Plasma FSH levels were undetectable at 1 week both in experimental and pair-fed animals. Pituitary FSH concentration was significantly reduced at 2 weeks and significantly increased at 4 weeks in the experimental rats when compared with the controls fed ad lib. Histological examination of the testes showed that controls fed ad lib. and pair-fed had reached full spermatogenesis at 4 weeks after the 1st injection (51 days of age); spermatogenesis of experimental animals was usually blocked at the stage of pachytene spermatocytes. In conclusion, depletion of brain 5-HT inhibited body and brain growth and sexual maturation partly through the ensuing anorexia and malnutrition, but possibly also through a specific decrease in synthesis and/or secretion of GH and FSH.

ISSN:0028-3835    

DOI:10.1159/000122254

出版商:S. Karger AG    

年代:1974

数据来源: Karger

摘要:

The effect of ketamine, a centrally-acting, nonbarbiturate anesthetic, on plasma corticosterone was studied in male rats. Ketamine administered intraperitoneally (i.p.) at anesthetic and subanesthetic doses (120–15 mg/kg) elicited corticosterone responses of the same magnitude as a pharmacological dose of ACTH. The plasma corticosterone response to ketamine was abolished in 24 h hypophysectomized rats and was blocked by dexamethasone (4 mg/kg i.p., 10 h prior to ketamine). The steroid response to ketamine was not significantly changed by prior systemic treatment with atropine or phentolamine. Pretreatment with propranolol or haloperidol, either singly or in combination, resulted in significant decreases in the corticosterone response to ketamine. These results suggest that the corticosterone response to ketamine is mediated through a facilitatory β-adrenergic and/or dopaminergic pathway or some hybrid thereof, and that ketamine is a convenient and useful agent for testing pituitary adrenal responsiveness in the r

ISSN:0028-3835    

DOI:10.1159/000122255

出版商:S. Karger AG    

年代:1974

数据来源: Karger

摘要:

Plasma concentrations of cortisol (F) and growthhormone were determined in samples obtained sequentially at 15 min intervals for 12 h night and 12 h day sessions in juvenile male monkeys (6–9.5 lb.) implanted with right atrial catheters. Electroencephalographic (EEG), electrooculographic (EOG), and electromyographic (EMG) activity were recorded. Cortisol was secreted episodically, increasing in frequency and concentration during the latter portion of the night and early morning hours. Growth hormone was also secreted episodically but bore no apparent relationship to either sleep stage or time of da

ISSN:0028-3835    

DOI:10.1159/000122256

出版商:S. Karger AG    

年代:1974

数据来源: Karger

摘要:

The neurohypophysis of the spayed femalerat previously injected with a single dose of 3H-estradiol took up and 75 min later retained significantly more radioactivity than the adenohypophysis. 86 to 92 % of the radioactivity in the neurohypophysis was chromato-graphically identified as estradiol. Cytosol fractions of rat neurohypophysis incubated with 3H-estradiol and subjected to Sephadex G-25 chromatography exhibited significant amounts of radioactivity bound to high molecular weight components. Treatment with dextran-coated charcoal of nuclei-free neurohypophysial homogenates incubated with 3H-estradiol of different specific activities uncovered a high affinity, low cupacity binding of estradiol to cytosol components. Testosterone and progesterone were about 60% as active as unlabeled estradiol in causing displacement of 3H-estradiol from high affinity binding sites. Estradiol uptake by the rat neurohypophysis exhibited significant in vivo 24-h variations, being maximal during day-time. Pinealectomy or superior cervical ganglionectomy caused increases in the uptake of estradiol by the neurohypophysis, which were partially reversed by the administration of melatonin.

ISSN:0028-3835    

DOI:10.1159/000122257

出版商:S. Karger AG    

年代:1974

数据来源: Karger

摘要:

Estradiol-binding capacity of the hypo-thalamus and parietal cortex, measured with tritiated estradiol, has been found to be significantly reduced in rats made anovulatory by exposure to continuous illumination when compared to controls of approximately equal weight maintained in a light-controlled (14 h light and 10 h dark) room. This finding suggests that constant light interferes with the normal replacement of estradiol-binding proteins in the brain. The decrease of the hypothalamic estrogen-receptors might account for the loss of the positive neurohormonal estrogen feedback inducing ovulatory LH release in the rat.

ISSN:0028-3835    

DOI:10.1159/000122258

出版商:S. Karger AG    

年代:1974

数据来源: Karger

摘要:

In order to study the role of brain biogenicamines in the regulation of ACTH secretion under basal and stress conditions, we examined changes in plasma corticosterone and hypothalamic CRF levels in male and female rats following either the intraventricular injection of biogenic amines or drug-induced changes in brain amine content. Various amounts (from 1 to 250 µg) of norepinephrine (NE), dopamine (DA), serotonin, carbachol and γ-aminobutyric acid (GABA) were injected into the lateral ventricle of the brain of conditioned unanesthetized rats through chronically-implanted cannulae. All the substances except GABA elicited a significant increase in ACTH secretion at the higher doses used. The stimulatory effects of centrally administered amines were partly abolished by prior treatment with reserpine or with reserpine along with Nembutal. Brain amines were depleted by pretreatment with either reserpine or 6-hydroxydopa-mine. In spite of the persistence of marked depletion of hypothalamic NE content, the basal circadian rhythm as well as stress-induced changes in both plasma corticosterone and hypothalamic CRF levels were preserved in almost the normal fashion. In addition, more than two-fold increases of brain amine concentration by pretreatment with a MAO inhibitor affected neither basal circadian rhythm nor a stress-induced increase in the plasma corticosterone. These observations suggest strongly that brain amines are of relatively little importance in the central regulation of ACTH secretion in the ra

ISSN:0028-3835    

DOI:10.1159/000122259

出版商:S. Karger AG    

年代:1974

数据来源: Karger

摘要:

Sodium pentobarbital (50 mg/kg) was administered oneach day of the estrous cycle to 4- and 5-day cyclic Long-Evans rats. In rats with 4-day cycles, the incidence of ovulation was significantly decreased when barbiturate was administered as a single injection at various times from 12.45 h on estrus to 12.45 h on diestrus-2. A delay in vaginal cornification and uterine ballooning measured on estrus, as well as decreased sexual receptivity on proestrus, was also found to result from barbiturate injections on diestrus-1, indicating a suppression of estrogen secretion. The deleterious effects of barbiturate treatment could be reversed by the simultaneous administration of gonadotropin. A generally similar pattern of blockade by barbiturate during this time period was found in 5-day cyclic rats, although the inhibitory effects were less than in 4-day cyclic rats. Furthermore, no inhibition of ovulation was found following drug administration on diestrus-3. The pattern of ovulatory blockade by barbiturate on the afternoon of proestrus was also generally similar in the 4- and 5-day cyclic rats. Again, however, more complete suppression was found in the 4-day cycle, and the duration of the inhibitory effects was more prolonged. It was concluded that the inhibitory effects of barbiturate administered early in the estrous cycle (estrus, diestrus-1 and diestrus-2) probably reflect a daily pattern of neural activity which is causally related to gonadotropin and estrogen secretion necessary for the final occurrence of ovulation.

ISSN:0028-3835    

DOI:10.1159/000122260

出版商:S. Karger AG    

年代:1974

数据来源: Karger

摘要:

Intracarotid injections of PGE1 into castrated-estrogen-pretreated female rats are followed by a rapid and prolonged release of LH, but have no important effects on FSH secretion. Intracarotid injections of PGF2α into the same type of animals induce a biphasic effect on LH release, and a marked and sustained hypersecretion of FSH. PGE1 given intracarotidly in normal male rats results in an elevation of plasma LH characterized by the occurrence of two peaks, but does not alter plasma FSH. Intracarotid injections of PGF2α in male rats have no effect on plasma LH levels, and cause a delayed elevation in plasma FSH. These results provide the first direct demonstration that PGs may induce the release of pituitary gonadotropin

ISSN:0028-3835    

DOI:10.1159/000122261

出版商:S. Karger AG    

年代:1974

数据来源: Karger

摘要:

Because the posterior pituitary gland is joinedto the anterior pituitary by the short portal vessels and con-tains both corticotropin and corticotropin-releasing factors, it could play a role in regulating adrenal hormone release. To clarify this, we studied the function of the brain-adrenal system, with and without the posterior pituitary, by determining glandular weights and plasma corticosterone concentrations. Studies were done under different conditions of anterior pituitary stimulation: (1) in the basal state; (2) after altered negative feedback (unilateral adrenalectomy); and (3) under different types and intensities of stress. All the studies were carried out in unanesthetized rats several weeks after either posterior hypophysectomy [i.e., neuro-intermediate lobectomy (NI-hypox)] or a sham operation. The findings demonstrate that the hypothalamic-anterior-pituitary-adrenal system functions normally in the absence of the posterior pituitary gland. Larger sex organs were found in unilaterally adrenalectomized, M-hypox male rats than were found in the sham-operated controls.

ISSN:0028-3835    

DOI:10.1159/000122262

出版商:S. Karger AG    

年代:1974

数据来源: Karger