Stress in rats causes acute release of hypothalamic somatostatin (SS) in median eminence (ME) that induces a marked and prolonged suppression of growth hormone (GH) secretion. This was evidenced by immunocytochemistry (ICC) and radioimmunoassay (RIA) in the present study. Adult female rats were decapitated under nonstress or for 30, 60, 120 and 180 min after 15 min leg restraint stress. The rabbit anti-SS was used to detect SS-14 and SS-28 containing 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 reproducible changes in cell bodies involved subsets of PeV neurons. Interestingly, these changes were largely reversed by 180 min. The results of the study demonstrate that stress cause acute changes in PO-AH, SS system and it appears that stress affects both SS synthesis and the secretion.