PERIPHERAL ADMINISTRATION OF PICROTOXIN AND BICUCULLINE STIMULATES INVIVO SOMATOSTATIN RELEASE FROM RAT MEDIAN-EMINENCE

The γ-Aminobutyric acid-A (GABAA) antagonist picrotoxin and bicuculline were administered to male rats to determine their effects on somatostatin (SRIF) release, measured in unanesthetized animals stereotaxically implanted with push-pull cannula in the median eminence (ME). I.p. injection (3 mg/kg) of picrotoxin (n=5) or bicuculline (n=6) significantly increased (35.4±10.8 vs 13.7±4.3 pg/15 min; P<0.03 and 38±3.5 vs 14±1.8 pg/15 min; P<0.001, respectively) SRIF release from the ME compared to baseline levels measured in the same animals. In contrast, with local perfusion of picrotoxin, (10-4 to 10-6 M) SRIF release from the ME was not affected. These data suggest a physiological endogenous inhibitory tone of GABA on SRIF release. © 1990.