N-METHYL-D-ASPARTATE RECEPTOR INVOLVEMENT IN DEXAMETHASONE AND STRESS-INDUCED HYPOTHALAMIC SOMATOSTATIN RELEASE IN RATS

The median eminence (ME) push-pull perfusion technique was used in thi s work and the results clearly showed that ip. administration of MK-80 1 (4 mg/kg), a specific N-methyl-D-aspartate (NMDA) receptor antagonis t, totally abolished dexamethasone (Dex) (300 mu g/100g i.p. injected) and immobilization stress-induced hypothalamic somatostatin release i n adult male rats. We also observed that glutamate from median eminenc e-hypothalamic medio basal (ME-MBH) complex, measured by high performa nce Liquid chromatography (HPLC), exhibited a conspicuous secretory pa ttern, with the total amount released not modified by Dex administrati on. This indicates that Dex and stress-induced somatostatin (SS) secre tion is not mediated by endogenous glutamate variations but likely by activation of NMDA receptors.