Acute and transient effects of stress on immunoreactive somatostatin cell bodies and fibers in the preoptic-anterior hypothalamus and median eminenceof female rats

Stress in rats causes acute release of hypothalamic somatostatin (SS) in me dian eminence (ME) that induces a marked and prolonged suppression of growt h hormone (GH) secretion. This was evidenced by immunocytochemistry (ICC) a nd radioimmunoassay (RIA) in the present study. Adult female rats were deca pitated under nonstress or for 30, 60, 120 and 180 min after 15 min leg res traint stress. The rabbit anti-SS was used to detect SS-14 and SS-28 contai ning cell bodies with ICC in preoptic-anterior hypothalamus (PO-AH). At 30, 60, 120 min after stress, there was marked decrease in the number and size of subsets of SS cell bodies. RIA demonstrated striking increase in SS in ME and significant decrease in GH of the portal blood. The most reproducibl e changes in cell bodies involved subsets of PeV neurons. Interestingly, th ese changes were largely reversed by 180 min. The results of the study demo nstrate that stress cause acute changes in PO-AH, SS system and it appears that stress affects both SS synthesis and the secretion.