摘要:

An in vitro perifusion system was used to investigate the spontaneous luteinizing hormone (LH) release from 10 human fetal (21–23 weeks of gestation) and 1 adult female pituitaries. The pattern of LH release from fetal pituitaries (n = 6) exhibited a remarkable pulsatile character with a mean (±SE) pulse interval of 12.7 + 1.7 min. The mean pulse amplitude was 5.2 ± 0.9 mlU with a nadir to peak increment of 69.5 ± 6.4%. The mean LH release rate was 12.3 ± 3.3 mIU/2 min. Blockade of calcium activity with 0.1 mM verapamil and 4 mM EGTA suppressed the frequency (from 1 pulse/12–20 min to 1 pulse/50–100 min) and amplitude (from 5.4–5.7 mlU to 1.4–2.1 mlU) of this spontaneous pulsatile LH release (n = 2). Administration of 8 nMgonadotropin-releasing hormone induced 255 and 954% increases in LH secretion (n = 2). Each quarter of an adult human pituitary also secreted LH in a pulsatile fashion, with a pulse interval of 15.2 ± 5.6 min, a pulse amplitude of 5.4 ± 0.6 mlU, a nadir to peak increment of 67.5 ± 5.2%, and an overall release rate of 14.8 ± 0.9 mIU/2 min. These studies demonstrate that LH release from the isolated human pituitary in vitro is characterized by high-frequency/low-amplitude pulses, independent of hypothalamic stimulation. Accordingly, this spontaneous calcium-mediated pulsatile LH release apparently reflects the activity of an intrinsic intrapituitary pulse-gen

ISSN:0028-3835    

DOI:10.1159/000124765

出版商:S. Karger AG    

年代:1987

数据来源: Karger

摘要:

Corticosterone (CORT) binds to two receptor systems in rat brain: the type I CORT-preferring receptor (CR) and the type II glucocorticoid receptor (GR). Discrimination between the two receptor types can be achieved with the ‘pure’ synthetic glucocorticoid RU 28362. In this study, we show that the binding capacity of GR in the rat hippocampus exhibits a strikingly different response from CR to adrenalectomy (ADX), chronic steroid replacement, hypophysectomy (HYPOX) and during circadian variation. Under those experimental conditions neither receptor site showed changes in binding affinity. After ADX, CR number remained relatively constant for a period of 13 days, while GR capacity increased by 133%, a level which was reached 5 days post-surgery. CR capacity showed circadian variation, since CR number was 65% higher in the evening than in the morning. GR capacities at those two time points were not significantly different. Replacement with subcutaneous CORT implants (100-mg pellets) for 7 days following ADX rats did not affect CR number, but caused a 38% decrease in GR number compared to control animals (cholesterol-treated, 7-day-ADX rats). On the other hand, dexamethasone (DEX) implants (5-, 15-, 25-mg pellets) elicited a dose-dependent increase in CR capacity (up to 99%) and a dose-dependent decrease in GR capacity (40–44%). Finally, 2 weeks after HYPOX, CR and GR numbers were increased by 60 and 38%, respectively. We conclude that the type II GR capacity responds in an autoregulatory manner to changes in circulating plasma glucocorticoid levels, while type I CR doe

ISSN:0028-3835    

DOI:10.1159/000124766

出版商:S. Karger AG    

年代:1987

数据来源: Karger

摘要:

The total number of LHRH cells and the distribution of LHRH cell morphological subtypes (classified as smooth or irregular LHRH cells) was investigated in adult male and female rats that received neonatal gonadectomies using light- and electron-microscopic immunocytochemistry. An identical number of immunoreactive LHRH cells (about 1,200) was observed in both treated and control animals. Both LHRH cell subtypes were present in treated animals, and the total number of each LHRH cell subtype and their distributions were similar to that seen in the control animals. At the EM level, LHRH cell subtypes from gonadectomized animals had similar morphological characteristics as have been described for normal adult rats. Synapses were present on both smooth and irregular LHRH cells of treated animals. These data indicate that the removal of gonadal steroids shortly after birth does not alter the overall LHRH cell number and distribution, nor the development of characteristic LHRH cell morphologies.

ISSN:0028-3835    

DOI:10.1159/000124767

出版商:S. Karger AG    

年代:1987

数据来源: Karger

摘要:

Electron-microscopic immunocytochemistry of serial thin sections showed that, in normal rats, approximately 50% of corticotropin-releasing factor (CRF) axons in the external zone of the median eminence contained vasopressin (AVP) and AVP precursor-derived peptides coexistent in the same secretory vesicles as CRF. The other 50% of the CRF axons contained little or no detectable AVP or AVP precursor-derived peptides. Differential activation of these subpopulations of CRF axons could provide a mechanism by which levels of CRF and AVP in portal plasma could be varied independently.

ISSN:0028-3835    

DOI:10.1159/000124768

出版商:S. Karger AG    

年代:1987

数据来源: Karger

摘要:

The distributions of perikarya exhibiting human somatocrinin (hGHRF) and neuropeptide Y (NPY) like immunoreactivities (IR) were compared in the arcuate nucleus of colchicine-treated rats. The majority of hGHRF perikarya was found to exhibit simultaneously NPY IR, while virtually no NPY IR was detected in the external layer of the median eminence. It is suggested that the majority of the hGHRF neurons of the rat arcuate nucleus constitutes a tubero-extra-infundibularly projecting system.

ISSN:0028-3835    

DOI:10.1159/000124769

出版商:S. Karger AG    

年代:1987

数据来源: Karger