Chronic stress affects in vivo hypothalamic somatostatin release but not in vitro GH responsiveness to somatostatin in rats.

One week after stereotaxical implantation of a push-pull cannula into the median eminence (ME), rats were stressed by immobilization for 2 h daily for 7 days. Thereafter, ME was perfused for 1 h in basal, stress and recovery conditions, respectively, and somatostatin (SRIH) was measured in perfusate fractions. Pituitaries were in vitro perifused to assess GH responsiveness to SRIH. In the stressed group, basal SRIH release was significantly higher than in the control group and stress caused a significant sharp peak in neurohormone release. GH responsiveness to SRIH was not affected in pituitaries obtained from stressed donors. High SRIH levels secreted under chronic stress thus did not impair the GH pituitary response to SRIH.