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Regulation of growth hormone and thyrotropin secretion by somatostatin system in rat brain


, : Regulation of growth hormone and thyrotropin secretion by somatostatin system in rat brain. Neuroendocrinology 42(3): 218-225

Somatostatin inhibits growth hormone (GH) and thyrotropin (TSH) secretion in the rat. Previous studies have shown that small discrete lesions of the periventricular hypothalamic (PV) and medial basal amygdaloid (AMG) nuclei, which contain high concentrations of somatostatin neurons, reduce somatostatin-like immunoreactivity (SLI) in the median eminence (ME) by approximately two thirds and one third, respectively. The present study assessed the function of the PV and AMG somatostatin systems in the regulation of basal episodic GH and TSH secretion. Three experiments were performed in freely behaving, chronically cannulated adult male rats. In experiment 1, bilateral electrolytic lesions (20 mC) were placed in the PV at the level of the paraventricular nucleus. In experiment 2, bilateral thermal lesions (55.degree. C .times. 1 min) were placed in the AMG. In experiment 3, thermal lesions were placed in both the PV and AMG (PV/AMG). Blood samples were removed from animals every 15 min for 5.5 h 14-21 days postoperatively. The ME was microdissected for determination of SLI content. PV, AMG and PV/ASMG lesions reduced ME SLI by 59, 26, and 91%, respectively. PV or AMG lesions had no effect on the amplitude or frequency of GH secretory peaks, GH trough levels or the total amount of GH secreted, whereas combined PV/AMG lesions reduced GH peak levels. Lesions of the AMG caused a 34% increase in mean plasma TSH levels, while PV or PV/AMG lesions reduced TSH. The latter effect was probably caused by damage to thyrotropin-releasing hormone neurons and/or axons, which are also located in the PV region. These results suggest that (1) PV and AMG somatostain systems may not have a significant role in the regulation of basal episodic GH secretion and (2) the putative AMG somatostain system exerts a significant inhibitory influence on TSH secretion.

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Accession: 006288288

PMID: 2869424

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Related references

Terry, L.C.; Crowley, W.R., 1986: Regulation of growth hormone and thyrotropin secretion by somatostatin systems in rat brain. Somatostatin inhibits growth hormone (GH) and thyrotropin (TSH) secretion in the rat. Previous studies have shown that small discrete lesions of the periventricular hypothalamic (PV) and medial-basal amygdaloid (AMG) nuclei, which contain high con...

Conte Devolx B.; Giraud P.; Gillioz P., 1979: Physiological role of thyrotropin releasing hormone and somatostatin in the control of thyrotropin and growth hormone secretion in the neo natal rats. Acta Endocrinologica Supplementum (225): 229

Critchlow, V.; Abe, K.; Urman, S.; Vale, W., 1981: Effect of lesions in the periventricular nucleus of the preoptic-anterior hypothalamus on growth hormone and thyrotropin secretion and brain somatostatin. Two experiments were performed to study the role of somatostatin (SRIF) neurons of the preoptic-anterior hypothalamic area (PO-AHA) in regulating growth hormone (GH) and thyrotropin (TSH) secretion in rats. Small lesions were placed in the periven...

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