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 periventricular (PV) zone and blood was collected at 24 h and 15 days after surgery. Blood samples were obtained at 3 min and at 15 min after ether exposure for assessing non-stress levels, respectively, of plasma GH and TSH. Non-stress blood samples were also collected at decapitation at 4 weeks. The brains from the first experiment were dissected and processed for measuring SRIF content in several regions. At 24 h and 15 days, non-stress GH and TSH levels were significantly elevated in rats with PV lesions. Stress-induced decrements in GH levels persisted in all groups. Although non-stress plasma GH and TSH levels returned to normal in lesioned rats at 4 weeks, SRIF content was decreased 83% in the median eminence and 33% in the hypothalamus. These results show that discrete lesions in the PV zone of the PO-AHA cause transient elevations in non-stress secretion of GH and TSH and that normal levels of such secretion can be reinstated despite reductions of SRIF in the median eminence and hypothalamus.
D000818:Animals; D001921:Brain / Q000378:metabolism*; D005260:Female; D013006:Growth Hormone / Q000097:blood / Q000378:metabolism*; D007031:Hypothalamus / Q000502:physiology*; D011301:Preoptic Area / Q000502:physiology*; D051381:Rats; D013004:Somatostatin / Q000378:metabolism*; D013972:Thyrotropin / Q000097:blood / Q000378:metabolism*; D014018:Tissue Distribution
D013004:Somatostatin; D013972:Thyrotropin; D013006:Growth Hormone