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, stres s and recovery conditions, respectively, and somatostatin (SRIH) was m easured in perfusate fractions. Pituitaries were in vitro perifused to assess GH responsiveness to SRIH. In the stressed group, basal SRIH r elease was significantly higher than in the control group and stress c aused a significant sharp peak in neurohormone release. GH responsiven ess to SRIH was not affected in pituitaries obtained from stressed don ors. High SRIH levels secreted under chronic stress thus did not impai r the GH pituitary response to SRIH.