[A study of the regulatory role of GABA on the LHRH release in the median eminence of rats].

The present study was undertaken to observe the effect of GABA and NA on LHRH neuronal terminals in the median eminence (ME). The results showed that GABA (10(-6) mol/L) significantly increased LHRH and NA release from ME, i.e., respectively from 27.3 +/- 2.5 pg/100 microliters to 150.4 +/- 27.9 pg/100 microliters and from 50.9 +/- 4.2 pg/100 microliters to 105.5 +/- 19.1 pg/100 microliters (both P less than 0.01 vs control group). These effects of GABA could be blocked by bicuculline. When bicuculline and GABA (10(-6) mol/L) were added into the ME, the secretion of LHRH decreased to 18.2 +/- 1.9 pg/100 microliters and that of NA to 43.9 +/- 3.4 pg/100 microliters. The effect of GABA on LHRH release may be mediated by NA. When endogenous NA was depleted by reserpine, GABA increased LHRH secretion only by 26.5% instead of 451.9% as in the normal animal.