摘要:

The purpose of this study was to determine the effects of destroying somatostatin (SRIF) neurons of the periventricular (PV) nucleus of the hypothalamus on the pulsatile pattern of growth hormone (GH) secretion in female rats. At 6–10 days after placement of PV lesions, blood samples collected every 15 min for 3–4 h showed an elevation in baseline GH levels and an increase in the amplitude of GH secretory peaks; the frequency of pulses was not affected. These changes were associated with an increase in mean integrated plasma GH levels. The alterations appeared transient because nonstress plasma GH levels were normal in two blood samples collected between 6 and 17 weeks after lesion placement and at autopsy at 17 weeks. Stress-induced suppression of GH secretion was also unaffected by the PV lesions. These lesions severely compromised the SRIF system that projects to the median eminence because the median eminence content of SRIF was approximately 85% depleted in the lesioned group. These results confirm that the hypothalamic PV nucleus is essential for maintaining most of the SRIF in the median eminence and demonstrate that damage to the PV nucleus causes transient alterations in the pulsatile pattern of GH secretion. However, the PV nucleus does not appear to play a major role in driving pulsatile GH secret

ISSN:0028-3835    

DOI:10.1159/000124202

出版商:S. Karger AG    

年代:1985

数据来源: Karger

摘要:

The parenchymal cells of the pars intermedia (PI) and corticotrophs of the pars distalis (PD) synthesize pro-opiomelanocortin (POMC), which, through posttranslational processing, gives rise to a group of structurally related peptides, including MSHs, ACTH, CLIP, LPHs and endorphins. We investigated the control of release of these peptides using an in vitro system. We perifused either intact neurointermediate lobes (NI) or PD halves obtained from rats. Perifusion medium and tissue extracts were subjected to a battery of bioassays (BA) and radioimmunoassays (RIA) (including MSH-BA, α-MSH-RIA, ACTH-BA, ACTH-RIA, LPH-RIA) and a receptor-binding assay for morphine-like activity (MLA). The relative amounts of released peptide activities were examined under basal conditions and after challenging with synthetic ovine corticotrophin-releasing factor (CRF) and somatostatin. CRF stimulated the release of all assayed peptides from both the PD and PI in a dose-related manner. Stimulated release was immediate (within 3 min), constant, reversible and repeatable. Somatostatin (up to 100 ng/ml) did not alter basal release from either PD or PI. Somatostatin did block CRF-induced release from the PI but not from the PD. These observations support an action of both CRF and somatostatin in the control of secretion of POMC-derived peptides from the PI

ISSN:0028-3835    

DOI:10.1159/000124203

出版商:S. Karger AG    

年代:1985

数据来源: Karger

摘要:

An in vitro bioassay was used to characterize the pattern of follicle-stimulating hormone (FSH)- and luteinizing hormone (LH)-releasing activities in the anterior (AH) and medial basal hypothalamus (MBH) during proestrus (P) and estrus (E) in the hamster. Regularly cycling hamsters were decapitated at 12.00, 16.00, 20.00 and 23.00 h of P and 02.00, 05.00, 08.00, 11.00, 14.00 and 17.00 h of E and sera assayed for FSH and LH. Neutralized extracts of the AH and MBH were incubated with a hemipituitary (HP), which was obtained from estrogen- and progesterone-primed ovariectomized rats. The incubation media were assayed for FSH and LH and the results expressed as nanograms of gonadotropin released per milligram HP. There was a surge of serum FSH and LH at 16.00 h of P and a surge of serum FSH only on E. LH-releasing activity in the AH and MBH declined late on P. This activity in the MBH increased by 08.00 h of E. FSH-releasing activity declined markedly in the MBH early on E when serum levels of FSH, but not LH, were rising. Conversely, low serum levels of FSH and high FSH releasing activity were found in the AH and MBH of animals with a chemically induced lesion of the arcuate nucleus. These data suggest that an FSH-releasing hormone may play an important role in the neuroendocrine control of FSH release.

ISSN:0028-3835    

DOI:10.1159/000124204

出版商:S. Karger AG    

年代:1985

数据来源: Karger

摘要:

In previous studies we obtained evidence that serotonin release by p-chloroamphetamine (PCA) causes an increase in corticosterone secretion but that this effect is not mediated via the raphe nuclei in the midbrain. In contrast, PCA-induced prolactin secretion was abolished by dorsal raphe lesions. In the present study, posterolateral cuts which interrupted caudal inputs to the hypothalamus attenuated the effect of PCA on plasma prolactin but did not block the PCA-induced increase in plasma corticosterone levels. Large lesions of the mediobasal hypothalamus produced a significant reduction of plasma corticosterone concentration but did not completely prevent the effect of PCA on corticosterone secretion. Hypophysectomy performed 24 h before sacrifice caused a marked decrease in plasma corticosterone levels but did not completely abolish the effect of PCA. These results suggest that PCA also stimulates corticosterone secretion via a direct action on the adrenal gland. The lesions in the mediobasal hypothalamus caused an increase in plasma prolactin concentration, and in these rats, PCA suppressed rather than stimulated prolactin secretion. This suggests that the known weak dopamine agonist activity of PCA is exposed when the effects of serotonin release in the brain are eliminated.

ISSN:0028-3835    

DOI:10.1159/000124205

出版商:S. Karger AG    

年代:1985

数据来源: Karger

摘要:

Conscious adult male rats bearing jugular cannulae were injected with either normal rabbit serum (NRS) or with serum containing antibodies to both oxytocin (OT) and arginine vasopressin (AVP). In the NRS-treated group, plasma levels of OT, AVP and immunoreactive glucagon (IRG) were significantly elevated 10 min after hemorrhage (2.3 ml/100 g body weight over 5 min) whereas hyperglucagonemia was not detected in the antiserum-treated group until 30 min posthemorrhage. In animals which were deprived of water during the experiment, plasma IRG in the antiserum-treated group reached only 40% of the levels in the NRS-treated controls. These results suggest that hemorrhage-induced elevations in circulating AVP and/or OT contribute to increased release of glucagon by the endocrine pancreas consistent with previous demonstration of glucagonotropic activity of synthetic neurohypophysial peptides.

ISSN:0028-3835    

DOI:10.1159/000124206

出版商:S. Karger AG    

年代:1985

数据来源: Karger

摘要:

The role of central corticotropin-releasing factor (CRF) in the regulation growth hormone (GH) secretion was studied in freely moving conscious male rats with indwelling intra-atrial and intracerebroventricular (i.c.v.) cannulae. GH measurements in blood samples obtained every 20 min from 10.00 to 14.00 h in control animals injected with saline either intravenously (i.v.) or into the lateral cerebral ventricle revealed that spontaneous GH secretion was pulsatile, and occurred regularly at around 12.00 h. When ovine CRF (10 µg) was injected i.c.v., spontaneous GH secretion was inhibited (mean plasma GH [11.20–13.00 h]: 20 ± 7 ng/ml vs. control: 126 ± 22 ng/ml, p < 0.01). In contrast, the intravenous injection of CRF (10 µg) did not affect spontaneous GH secretion (mean plasma GH [11.20–13.00 h]: 162 ± 25 ng/ml vs. control: 193 ± 31 ng/ml). This GH suppressive action of central CRF was blocked by the i.v. injection (0.5 ml) of antisomatostatin serum (AS), but not of normal sheep serum (NS), (mean plasma GH [11.20–13.00 h]: NS + CRF: 15 ± 2 ng/ml vs. AS + CRF: 202 ± 30 ng/ml, p < 0.01). The mean plasma GH value [11.20–13.00 h] in animals receiving AS and CRF was not significantly different from those in animals receiving saline (i.v.) together with AS. These results suggest a potential inhibitory role of central CRF in the regulation of spontaneous GH secretion in the rat which is mediated by the stimulation of hypothalam

ISSN:0028-3835    

DOI:10.1159/000124207

出版商:S. Karger AG    

年代:1985

数据来源: Karger

摘要:

Fluorescence histochemical and immunocytochemical techniques were used to investigate morphologic correlates of the relationship between catecholamine varicosities and vasopressin-containing perikarya in an animal model of vasopressin excess, the nephrogenic diabetes insipidus mouse. Our results show hypertrophy and increased immunoreactivity in vasopressin neurons in these mice were accompanied by a marked increase in the density and to some extent the fluorescence intensity of catecholamine varicosities within the supraoptic nucleus. These results further support the concept of functional interactions between catecholamine and vasopressin neurons and raise the possibility that the target neuron, or one of its products, perhaps vasopressin, either exerts a trophic influence on the catecholamine innervation pattern of the supraoptic nucleus or enhances catecholamine content in existing fibers and terminals.

ISSN:0028-3835    

DOI:10.1159/000124208

出版商:S. Karger AG    

年代:1985

数据来源: Karger

摘要:

Cystatin C, a protein inhibitor of lysosomal cysteine proteinases, was demonstrated by immunohistochemical techniques to be present in most luteinizing hormone- (LH-)containing cells in simian and human adenohypophyses. Immunoreactivity of cystatin C was also found in simian adrenocorticotrophic hormone- (ACTH-)containing cells localized to an area corresponding to the pars intermedia but not in the ACTH-containing cells of the anterior pituitary lobe of monkey. No immunoreactivity of cystatin C was detected in the growth hormone- (GH-) and prolactin-containing cells of monkey and man.

ISSN:0028-3835    

DOI:10.1159/000124209

出版商:S. Karger AG    

年代:1985

数据来源: Karger

摘要:

Bromocriptine (CB 154), a potent agonist upon the D-2 receptor, blocks the proliferation of the mammotrophs and the elevation of serum prolactin concentration induced by chronic exposure of male Fisher 344 rats to diethylstilbestrol (DES). Fluphenazine, a dopamine receptor antagonist, blocks these effects of CB 154. We conclude that a D-2 receptor occurs on the proliferating mammotroph of the male Fisher 344 rat and that stimulation of this receptor inhibits prolactin release and stops the DES-induced proliferation of these cells.

ISSN:0028-3835    

DOI:10.1159/000124210

出版商:S. Karger AG    

年代:1985

数据来源: Karger

摘要:

The effects of 3 compounds previously known to alter the adenylate cyclase activity in various tissues were tested on rat pituitary. Forskolin increased while RMI 12,330 A and SQ 22,536 decreased enzyme activity of pituitary homogenates. Forskolin (10–5M) promoted in cultured cells a massive synthesis of cyclic adenosine monophosphate (cAMP) and intense output of the nucleotide in the medium; at the same concentration, RMI 12,330 A decreased the cell content of cAMP while release was unaffected, and SQ 22,536 exerted no effect on the cyclic nucleotide amount of both cell and medium. The basal release of plated total cells or enriched gonadotropes was slightly stimulated by forskolin (10–7–10–5M) though the level of stimulation never attained the one produced by 10–7M luteinizing hormone-releasing hormone (LHRH); it was affected neither by RMI 12,330 A (10–7–10–5M) nor by SQ 22,536 (10–7–10–4M). The LHRH-stimulating effect was slightly amplified during the 1st h (sensitivity response of cells) by low concentrations of forskolin (10–7 and 10–6M) but the overall luteinizing hormone (LH) release after 4 h of incubation (capacity response of cells) was unmodified. Higher concentrations of the diterpene inhibited the LHRH effect as seen with total cells and with enriched gonadotropes. RMI 12,330 A at 10^5M significantly inhibited the LHRH-promoted LH release from total cells and from gonadotropes but a higher concentration (10–4M) promoted a large unspecific release that masked the LHRH effect. SQ 22,536 never modified the cell response to LHRH, whatever the drug concentration. We thus conclude that LH release is partly cAMP dependent, the cyclic nucleotide acting during the very early phase of LHRH action (on the readily releasable LH pool, i.e. sensitivity response) but exerting no effect during the 2nd step (mobilization of LH stores, i.e. capacity response). Forskolin (10–7 10–5M) stimulated prolactin (PRL) release, but it was unable to overcome the dopamine-(DA-)inhibiting effect though the adenylate cyclase was stimulated by 10–6M of the diterpene in the presence of 10^7 M DA. 10–5M of RMI 12,330 A inhibited PRL release as efficiently as 10–7M DA did. SQ 22,536 exerted no effect, whatever the drug concentration. These results confirm the participation of the cAMP-generating system in PRL release; however, activation of the adenylate cyclase is not sufficient to stimulate hormone release o

ISSN:0028-3835    

DOI:10.1159/000124211

出版商:S. Karger AG    

年代:1985

数据来源: Karger