摘要:

The immunocytological method was used to investigate whether vasoactive intestinal peptide (VIP) is present in the pituitary gland and to localize the peptide at the cellular and subcellular levels. Pituitaries of Wistar male and female rats (Iffa Credo) were fixed in glutaraldehyde 2.5% and postosmicated and frozen in liquid nitrogen. Ultrathin slices, obtained by cryo-ultramicrotomy were incubated with the antiserum. The antigen-antibody reaction was detected by peroxidase-antiperoxidase complexes revealed by 4-chloro-1-naphtol. The prolactin (PRL)-secreting cells were identified by using an anti-oPRL antiserum. The PRL immunoreactivity was localized in secretory granules of irregular shapes. An anti-VIP serum was used which neither cross-reacted with the several fragments of VIP molecule nor with peptides from gut or hypothalamus. The VIP immunoreactivity obtained with this antiserum, was observed in PRL cells only but never in somatotropic, gonadotropic, corticotropic and thyrotropic cells. The immunoreactivity was localized in the cytoplasmic matrix between and around the secretory granules but not in the organelles, and in the nucleus distributed all over the euchromatin near to the heterochromatin regions. No reaction was observed by using either nonimmune serum or anti-VIP antiserum incubated with VIP. No modification of VIP immunoreactivity was observed by using anti-VIP antiserum incubated with somatostatin, gonado- or thyroliberin. These data (1) provide immunocytological evidence for presence of VIP in pituitary gland; (2) indicate the presence of this peptide in one particular pituitary cell type, and (3) support the hypothesis that VIP could have a direct effect on the control of PRL secretion.

ISSN:0028-3835    

DOI:10.1159/000123282

出版商:S. Karger AG    

年代:1982

数据来源: Karger

摘要:

Following bilateral adrenalectomy in adult male rats, there occurs a pattern of triphasic change in basal plasma concentration of radioimmunoassayable ACTH. Plasma ACTH is markedly elevated at 2 h, has returned down almost to normal at 20 h and is again markedly elevated 96 h after adrenalectomy. We have examined serotonin (5HT) synthesis rates in several brain regions, anterior hypothalamus, posterior hypothalamus, and brain stem, at these times after adrenalectomy using the accumulation of 5-hydroxytryptophan (5HTP) after inhibition of aromatic L-amino acid decarboxylase with m-hydroxybenzylhydrazine. In both anterior hypothalamus and brain stem, decreased 5HT synthesis rates were observed at 2 and 96 h after adrenalectomy, but at 20 h 5HT synthesis rates were normal. This pattern was not observed in the posterior hypothalamus. Thus, we demonstrated inverse correlations between 5HT synthesis rates in anterior hypothalamus and brain stem, but not posterior hypothalamus, and basal plasma ACTH concentration throughout the period of triphasic change following adrenalectomy in adult male rats. Both the adrenalectomy-induced increases in plasma ACTH concentration and the adrenalectomy-induced decreases in brain 5HT synthesis rates were inhibited by treatment with dexa-methasone, suggesting that the changes resulted from glucocorticoid withdrawal. The data are consistent with a role of brain 5HT neurons with cell bodies in brain stem and nerve endings in anterior hypothalamus in the regulation of the triphasic changes in plasma ACTH concentration following adrenalectomy in rats.

ISSN:0028-3835    

DOI:10.1159/000123283

出版商:S. Karger AG    

年代:1982

数据来源: Karger

摘要:

Neurotensin stimulated prolactin (PRL) secretion from incubated rat hemipituitaries. Under the same conditions, the secretion of growth hormone, luteinizing hormone and follicle-stimulating hormone was not affected. The stimulation of PRL was dose dependent, with an apparent affinity of neurotensin of 0.56 + 0.12 nMand a maximal stimulation of 56.5±6.7%. The effect of neurotensin seemed to be independent of that of other PRL releasing factors. In fact, the stimulation of neurotensin and thyrotropin-releasing hormone (TRH) and also of neurotensin and vasoactive intestinal peptide were additive. The action of neurotensin on PRL cells does not appear to involve either dopamine or γ-aminobutyric acid receptors, since antagonists to these transmitters were found ineffective on PRL stimulation by neurotensin. PRL-releasing factor activity distinct from TRH has been described in fractions of hypothalamic extracts. Neurotensin, which is present in high amounts in the median eminence and has been measured in the adenohypophysis, is a candidate as a physiological PRL-releasing factor distinct from TR

ISSN:0028-3835    

DOI:10.1159/000123284

出版商:S. Karger AG    

年代:1982

数据来源: Karger

摘要:

Most of the corticotrophin-releasing factor (CRF) activity of normal rat median eminence (ME) extract binds to a neurophysin affinity column. The bound material contains the large and small factors, which we have previously demonstrated to be required together for full activity. Most of the CRF activity of Brattleboro rat ME extract, which contains as much CRF activity as the ME extract of a normal rat, does not bind to a neurophysin affinity column. The CRF activity of Brattleboro rat ME extract resides entirely in a large molecule as determined by Sephadex G-25 chromatography. The different properties of Brattleboro and normal rat CRF suggest that the CRF activity in the Brattleboro rat may result from a substance which is different from that in a normal rat.

ISSN:0028-3835    

DOI:10.1159/000123285

出版商:S. Karger AG    

年代:1982

数据来源: Karger

摘要:

These studies were conducted to determine the possible site of action at which estrogen ‘feminizes’ the pituitary luteinizing hormone (LH) response to orchidectomy (ORDX). When Silastic implants containing estradiol-17β (E2) were inserted 1 day prior to ORDX and subsequently removed 5 days later, characteristic increases in plasma LH and follicle-stimulating hormone (FSH) levels normally observed within 24 h after ORDX were completely (for LH) or partially (for FSH) prevented. Rather, gonadotropin patterns, especially LH, resembled patterns seen during a similar time interval after ovariectomy of female rats on diestrus-1, that is, increases in plasma FSH unaccompanied by rises in plasma LH. Although castration-induced increments in plasma gonadotropin levels were abated by prior E2 treatment of orchidectomized male rats, the responsiveness of the anterior pituitary gland to two intravenous pulse injections of luteinizing hormone-releasing hormone (LHRH) tested 6 and 8 h after removal of E2 capsules was markedly greater than pituitary LH responses to both pulse injections at similar times following ORDX. Pituitary FSH responses in E2-treated orchidectomized rats were higher only after the second LHRH injec

ISSN:0028-3835    

DOI:10.1159/000123286

出版商:S. Karger AG    

年代:1982

数据来源: Karger

摘要:

The pineal indole melatonin suppresses the neonatal rat luteinizing hormone (LH) and follicle-stimulating hormone (FSH) responses to LH-releasing hormone (LHRH), as shown in previous studies from this laboratory. We show in this study that the melatonin inhibition is a selective effect and is not due to general inhibition of pituitary function. The effects of the indole on the responses to thyrotropin-releasing hormone (TRH) and somatostatin (SRIF) and on basal pituitary hormone secretion were examined with cells in culture. Neonatal rat anterior pituitary cells dissociated with collage-nase and hyaluronidase were cultured overnight and distributed to 35-mm dishes at the time of use. For examination of melatonin effects on the response to releasing hormones, the cells were incubated for 3 h in control medium or medium containing LHRH (10–9-10–6M), TRH (10–10-10–6M), or SRIF (10–9-10–6M), either alone or in the presence of melatonin (10–8 or 10–6M). For examination of basal hormone secretion, the cells were incubated for 1.5, 3, 6, 15, or 24 h in either medium alone or medium containing melatonin (10–6M). Medium and cell lysate concentrations of LH, FSH, thyroid-stimulating hormone (TSH), prolactin (PRL) and growth hormone (GH) were determined by double antibody RIA. As previously, melatonin (10–8M) significantly suppressed LH and FSH release by all concentrations of LHRH. This concentration of the indole produced maximal suppression of both LH and FSH responses to LHRH.By contrast, melatonin at a 100-fold greater concentration (10–6M) had no effect on TRH stimulation of TSH or PRL release or on SRIF inhibition of GH release. Similarly, melatonin had no effect on basal release of TSH, PRL, or GH at the times examined. These findings show that melatonin inhibition of the gonadotroph response to LHRH

ISSN:0028-3835    

DOI:10.1159/000123287

出版商:S. Karger AG    

年代:1982

数据来源: Karger

摘要:

The distribution of γ-aminobutyric acid (GABA) nerve fibers and cell bodies in the rat hypothalamus and pituitary gland was immunohistochemically examined using antibodies against the GABA-synthesizing enzyme glutamate decarboxylase (GAD). A dense network of GAD-positive nerve fibers was observed to be essentially evenly distributed throughout the hypothalamus. A plexus of GABA terminals was also demonstrated both in the median eminence and within the posterior and intermediate lobes of the pituitary. Three distinct clusters of magnocellular GABA neurons were discovered in the posterior hypothalamus. In addition, GAD immunoreactive cell bodies were observed in many other hypothalamic nuclei, such as the arcuate nucleus and in the perifornical region. These results provide a morphological basis by which GABA of hypothalamic origin may regulate the neuroendocrine system

ISSN:0028-3835    

DOI:10.1159/000123288

出版商:S. Karger AG    

年代:1982

数据来源: Karger

摘要:

During night (11 p.m.–7 a.m.) blood was sampled in darkness via an indwelling intravenous catheter simultaneously with polygraphic sleep registration in 7 normal men. The nocturnal melatonin secretion patterns exhibited secretory episodes. Spontaneous waking episodes were shown to be significantly correlated to the occurrence of melatonin peaks (χc2 = 9.0, p < 0.005 Melatonin nadirs were significantly associated with rapid eye movement periods (χc2 = 12.8, p < 0.005) but not with other sleep stages evaluated by standard criteria. It is hypothesized that melatonin secreted in connection with arousals during night may in turn act to restore sleep in hum

ISSN:0028-3835    

DOI:10.1159/000123289

出版商:S. Karger AG    

年代:1982

数据来源: Karger

摘要:

Experiments were carried out to investigate the effect of intracerebroventricular administration of a prostaglandin synthesis inhibitor on the osmotic control of vasopressin (ADH) secretion. During ventriculocisternal perfusion with indomethacin (7.6 μg/min) or vehicle, dogs were infused intravenously with either 2.5 or 0.15 M NaCl. Hypertonic saline infusion elevated plasma osmolality approximately 60 mosm/kg H2O. In accordance, the plasma ADH concentration increased substantially in animals perfused ventriculocisternally with the vehicle (from 2.1 ± 0.7 to 7.3 ± 1.3 μU/ml); this response was markedly attenuated, however, in animals perfused with indomethacin (from 1.0 ± 0.2 to 2.2 ± 0.4 μU/ml). Isotonic saline infusion caused a decline in plasma ADH concentration which was similar in the indomethacin- and vehicle-perfused groups. Mean arterial blood pressure was unchanged during the experiments. In a companion study, ventriculocisternal perfusion with 152 ng PGE2/min was found to be as effective in stimulating ADH release in the presence of indomethacin as in its absence, indicating that the action of indomethacin in the first study was not nonspecific. The suppression of osmotically induced ADH release by intracerebroventricular indomethacin suggests that endogenous brain prostaglandins play a critical intermediary role in the osmotic control of ADH sec

ISSN:0028-3835    

DOI:10.1159/000123290

出版商:S. Karger AG    

年代:1982

数据来源: Karger

摘要:

A lesion of the medial basal hypothalamus (MBH) results in enhanced secretion of prolactin and reduced release of the other hormones from the anterior pituitary. We measured the volume percentage of the prolactin-secreting mammotrophs, stained immunocytochemically, under several experimental conditions to assess the morphological correlate of the high secretion of prolactin. In addition, gonadotrophs were stained both tinctorially with the periodic acid-Schiff reagent and immunocytochemically with antibodies to luteinizing hormone. Anterior pituitaries were studied from female rats which were:(1) cycling, (2) ovariectomized for 2 weeks, (3) ovariectomized for 2 weeks with a lesion of the MBH for 1. 14 or 21 days. The volume percentage of mammotrophs and gonadotrophs in the lateral, central and middle fields of the anterior pituitary was determined and this measurement was expressed relative to endocrine cellular area so that vascular space and necrotic regions would not be included in the assessment. Ovariectomy significantly decreased mammotroph and increased gonadotroph volume percentage when compared to the intact animal. MBH lesions had the opposite effect. At 14 and 21 days after a lesion, the volume percentage of mammotrophs was significantly greater than in the intact rat, while the volume percentage of gonadotrophs was identical to that observed in the intact rat. These data suggest that the elimination of the prolactin-inhibitory hormone(s) of the MBH results in hypertrophy and/or hyperplasia of mammotrophs. This effect occurs in the absence of ovarian steroids and may be of importance in the induction of prolactin-secreting pituitary adenomas. The data also support the hypothesis that destruction of gonadotropin-releasing hormone neuron terminals countermands the hypertrophy of gonadotrophs induced by ovariectomy.

ISSN:0028-3835    

DOI:10.1159/000123291

出版商:S. Karger AG    

年代:1982

数据来源: Karger