摘要:

The peroxidase-antiperoxidase immunocytochemical method was used to determine quantitatively the effects of gonadal steroids on the immunoreactive luteinizing hormone-releasing hormone (LHRH) content in the brain of male and female rats. In the male rat, gonadectomy decreased both the number of cell bodies and optical density of staining in cell bodies containing immunoreactive LHRH; decreased the percentage of area covered by LHRH fibers in the middle and caudal aspects of the median eminence (ME) but not the organum vasculosum lamina terminalis (OVLT), and decreased the number of LHRH fibers localized in the midbrain central gray (MCG). Since others have shown previously that gonadectomy increases the LHRH content of portal blood in the male rat, the results suggest that the decreased somal accumulation of LHRH and decreased LHRH content in fibers in the ME and MCG measured in the present study following loss of testicular steroids reflect increased LHRH release from the ME and MCG into the portal blood and brain, respectively.

ISSN:0028-3835    

DOI:10.1159/000123522

出版商:S. Karger AG    

年代:1983

数据来源: Karger

摘要:

Haloperidol, sulpiride, domperidone and apomorphine, drugs which influence dopamine (DA) receptors and in turn prolactin (PRL) secretion have been shown to induce parallel changes in medial basal hypothalamic (MBH) glutamate decarboxylase (GAD) activity and serum PRL levels. The possibility that PRL may be involved in the effects of the drugs on MBH GAD activity is suggested in view of the evidence that hypophysectomy completely prevents drug-induced MBH GAD activity changes and that hyperprolactinemia by anterior pituitary homograft results in a significant, although small, change in the enzymatic activity.

ISSN:0028-3835    

DOI:10.1159/000123430

出版商:S. Karger AG    

年代:1983

数据来源: Karger

摘要:

We had previously observed a circadian rhythm for serum TSH in male Sprague-Dawley rats (under a 12-hour light-dark cycle, light off at 19.00 h). In the present work the parameters of this previously observed TSH rhythm were determined over a year on a monthly basis. A circadian rhythm was detected for each month except April. From month to month, the amplitudes and acrophases of these rhythms were not significantly different, and a circannual rhythm was only established for the mean TSH concentration over the 24-hour period (mean hormonal value). We conclude that there is a constant circadian pattern for serum TSH fluctuations superimposed on a small basal circannual rhythm of the mean hormonal value.

ISSN:0028-3835    

DOI:10.1159/000123431

出版商:S. Karger AG    

年代:1983

数据来源: Karger

摘要:

To study the interactions of catecholestrogens with the catecholamine system we estimated the catecholamine concentrations and turnover rates in the anterior part of the mediobasal hypothalamus (AMBH) and medial preoptic area (MPO) following 2-hydroxyestradiol-17β (2-OHE2) or 2-hydroxyestrone (2-HOE1) treatment in castrated male and female rats. Serum concentrations of LH and prolactin were also measured. The turnover rates of catecholamines were calculated by monitoring the catecholamine loss 1 h after blocking the catecholamine synthesis with α-methyl-p-tyrosine. Dopamine, epinephrine and norepinephrine concentrations were measured by a radioenzymatic assay. In males, 2-OHE2 (50 µg/kg) and 2-OHE1 (50 µg/kg) resulted in decreased serum LH values (p < 0.05) 4 and 5 h after treatment. None of these 2-hydroxylated estrogens were able to alter serum prolactin levels significantly. There was a decline in epinephrine and norepinephrine concentrations in the AMBH. The greatest change in catecholamine turnover rates in response to catecholestrogen treatment also occurred in the AMBH. 2-OHE2 and 2-OHE1 reduced turnover rates of dopamine, norepinephrine and epinephrine in the AMBH. Only the dopamine turnover rate was affected in the MPO, where it increased following 2-OHE2 treatment. In females, only 2-OHE2 (50 µg/kg) was effective in decreasing serum LH (p < 0.05) and increasing prolactin (p < 0.01) levels. Dopamine and epinephrine concentrations as well as their turnover rates declined in the AMBH after treatment with catecholestrogens. The concentration and turnover rate of epinephrine also decreased in the MPO. There was no significant change in norepinephrine concentration or turnover rate. It is suggested that 2-hydroxyestrogens are possibly involved in mechanisms which are inhibitory to LH secretion and stimulatory to prolactin release. These actions appear to be partly mediated by catecholam

ISSN:0028-3835    

DOI:10.1159/000123523

出版商:S. Karger AG    

年代:1983

数据来源: Karger

摘要:

Feedback regulation of basal and stimulated release of prolactin (Prl) was studied in primary cultures of rat pituitary cells and in adult male rats bearing right atrial catheters. Exposure of cell cultures to ovine (o) Prl, which does not crossreact in the radioimmunoassay for rat (r) Prl, did not affect rPrl release during in vitro incubations. oPrl, 4 mg/kg, injected subcutaneously into male rats 4 h previously, significantly suppressed basal rPrl levels and blunted the rPrl response to ether (2 min), cimetidine (25 mg/kg i.v.), thyrotropin-releasing hormone (40 or 400 ng i.v.), or a low dose of metoclopramide (25 µg/kg i.v.). At a higher dose of metoclopramide (500 µg/kg i.v.), no effect of oPrl could be observed. These data support the hypothesis that Prl feedback control occurs within the central nervous system rather than at the pituitary and involves predominantly, if not exclusively, a dopaminergic mechanis

ISSN:0028-3835    

DOI:10.1159/000123432

出版商:S. Karger AG    

年代:1983

数据来源: Karger

摘要:

Bombesin-like peptides are present in the mammalian hypothalamus. It has previously been reported that synthetic bombesin elevates plasma growth hormone (GH) and prolactin (PRL) concentrations in rats. To investigate whether bombesin has a direct action on the pituitary gland we measured GH and PRL secretion from 5-day cultures of bovine anterior pituitary cells. We compared the effects of bombesin with those of a previously described synthetic pentapeptide which releases rat GH in vitro (GHRP) and with the effects of acetylcholine which stimulates bovine GH secretion. Bombesin stimulated GH but not PRL secretion from pituitary cultures during 90-min incubations. Maximal stimulation to 157 ± 16% of the control value was seen with 1.2 × 10-7M bombesin. Half-maximal stimulation occured with 5 × 10-9M bombesin. The pentapeptide GHRP also stimulated GH but not PRL secretion. Maximal stimulation to 207 ± 14% of the control value was seen with 1.3 × 10-5M GHRP. Half-maximal stimulation occurred with 10-7M GHRP. Acetylcholine stimulated secretion of both GH and PRL, both responses being abolished by the muscarinic antagonist atropine. Maximal stimulation with 10-4M acetylcholine was to 381 ± 33% of the control value for GH and to 134 ± 5% of the control value for PRL. The effects of bombesin and GHRP on GH secretion were not additive whilst the effects of both peptides were additive with those of acetylcholine. The data suggest that the synthetic GHRP peptide may possibly interact with native bombesin receptors on pituitary somatotrophs and that bombesin or a related peptide may act in vivo as a GH releasing

ISSN:0028-3835    

DOI:10.1159/000123433

出版商:S. Karger AG    

年代:1983

数据来源: Karger

摘要:

Cortisol levels in the serum and cerebrospinal fluid (CSF) were studied in ovariectomized, estrogen-treated monkeys during either prolonged hypercortisolemia or the more transient effects of a bolus injection of cortisol. Control (saline-treated) animals showed the expected diurnal rhythm in serum cortisol, but proportionately more cortisol was present in the CSF when serum levels were high (i.e. in the morning). Prolonged hypercortisolemia for up to 37 days was produced by either thrice daily injections of cortisol itself or single daily injections of ACTH1-24 in the morning. Both treatments produced disproportionately larger amounts of cortisol in the CSF than in the serum, and the CSF/serum cortisol ratio was increased. Furthermore, prolonged ACTH treatment caused a marked elevation in CSF cortisol in afternoon samples taken at 16.30 h compared with those at 10.00 h, in the absence of a similar change in serum cortisol levels. The relative importance of entry and clearance of cortisol in the CSF in these conditions was studied in several ways. ‘Free’ cortisol levels in serum (determined by equilibrium dialysis) were equal to CSF cortisol levels in control monkeys, but were less than those in the CSF of hypercortisolemic animals. Entry of cortisol into CSF after a bolus injection was rapid, but, unlike serum, CSF cortisol levels did not decline significantly over a 70-min sampling period and the delayed clearance from the CSF could account for some of the effects seen during hypercortisolemia. Neither high levels of prolactin (which is elevated together with cortisol in ‘stress’), induced by giving sulpiride, nor treatment with progesterone (which is also bound by corticosteroid binding globulin) altered the distribution of cortisol between blood and CSF. The concentrations of cortisol in the CSF therefore are regulated by factors influencing both its entry and clearance from the cerebral compartment. Neural tissues sensitive to cortisol are thus exposed to levels of this hormone that are both qualitatively and quantitatively different from those expected by direct extrapolation from serum

ISSN:0028-3835    

DOI:10.1159/000123434

出版商:S. Karger AG    

年代:1983

数据来源: Karger

摘要:

The present study was designed to determine the role of glucocorticoids in the mediation of the stimulatory effect of indomethacin (IM) on the hypothalamo-hypophyseal-adrenal axis. Intact male rats were treated with a single injection of either dexamethasone (Dex; 20 µg/100 g body weight), IM (5 mg/100 g body weight), or IM + Dex or their respective vehicles. In Dex-treated rats, ACTH and corticosterone (CS) were significantly reduced over a period of 20 h as compared to the vehicle-treated group. As we have previously demonstrated, injection of IM markedly elevated serum ACTH and CS for at least 20 h. Administration of Dex 2 h prior to IM treatment delayed the stimulatory effect of IM for 5 h; subsequently, however, Dex was without effect. In adrenalectomized rats, ether stress elicited a marked rise in serum ACTH levels. On the contrary, IM was completely ineffective in these rats. These studies suggest that the mode of action of IM in causing hypersecretion of ACTH and CS is by interfering with the negative feedback effects of the glucocorticoids

ISSN:0028-3835    

DOI:10.1159/000123435

出版商:S. Karger AG    

年代:1983

数据来源: Karger

摘要:

The release of LH in ovariectomized, estrogen-primed rats exposed to male or female rats was studied. The concentration of LH in the serum was measured in blood samples obtained by an indwelling jugular cannula. A blood sample was taken at 12.00 h and then every hour up to 18.00 h following exposure to another rat on the opposite side of a double wire mesh screen. LH in the serum of control non-exposed rats showed a small rise between 16.00 and 18.00 h as compared to earlier values. Rats exposed to intact or castrated male rats exhibited an enhanced release. Exposure to ovariectomized rats failed to induce any change in the release of LH but exposure to ovariectomized, estrogen-primed rats produced a significant increase. No effect on LH release was seen in animals exposed to a female diestrous rat or to a pregnant rat. Rats exposed to an empty cage which had been soiled by housing a male rat for 3 days, showed an enhanced release of LH similar to those exposed to a cage containing the male rat, indicating the importance of olfactory stimuli in the response. Ovariectomized rats whose vomeronasal organs had been removed or whose accessory olfactory bulbs were lesioned, failed to show any effect on the release of LH when exposed to a male rat. It is concluded that olfactory stimuli arising from male or female rats are capable of modulating the release of LH in female rats and that perception of these stimuli involves the vomeronasal organ-accessory olfactory bulb system.

ISSN:0028-3835    

DOI:10.1159/000123436

出版商:S. Karger AG    

年代:1983

数据来源: Karger

摘要:

The annual cycle of reproduction in the golden hamster (Mesocricetus auratus) is characterized by gonadal regression in response to decreasing daylengths in fall. However, hamsters become refractory to the inhibitory effects of short daylengths in late winter when gonadal recrudescense occurs. Our results show that addition of tryptophan to the diet of photorefractory hamsters causes them to respond to short daylengths in a manner similar to photosensitive hamsters in winter. Similar tryptophan treatment did not influence testes weights and fat stores of hamsters maintained on long daylengths.

ISSN:0028-3835    

DOI:10.1159/000123437

出版商:S. Karger AG    

年代:1983

数据来源: Karger