P. Prunet et al., GABAERGIC CONTROL OF PROLACTIN-RELEASE IN RAINBOW-TROUT (ONCORHYNCHUS-MYKISS) PITUITARIES IN-VITRO, Fish physiology and biochemistry, 11(1-6), 1993, pp. 131-137
The involvement of gamma-aminobutyric acid (GABA) in the control of pr
olactin (PRL) release was investigated in rainbow trout using both per
ifused pituitary fragments and pituitary cells in primary culture. In
our perifusion system, infusion of GABA (10(-6) to 10(-4) M) caused an
inhibition of PRL release (between 20 and 40%). Administration on per
ifused pituitary fragments of 3APS, a GABAa agonist, mimicked this inh
ibitory effect. Moreover, bicuculline, a specific antagonist of GABAa
receptors, totally abolished GABA effect. When tested on cultured pitu
itary cells during 40h exposure, GABA (10(-5) M) caused a significant
decrease in PRL release (24.5 %). Baclofen, a specific agonist for GAB
Ab receptor tested at 10(-6) and 10(-5) M, also inhibited PRL released
from cultured pituitary cells. These results demonstrate that GABA in
hibits PRL release by acting directly on pituitary cells and that prob
ably both types of GABA receptor (a and b) are involved in this regula
tion.