Ontogenic expression of anterior pituitary GABA(B) receptor subunits

gamma -Aminobutyric acid (GABA) is involved in the neuroendocrine control o f hypophyseal secretion, acting both in the central nervous system and dire ctly at the pituitary. We have characterized the properties of anterior pit uitary GABA(B) receptors. In this work the ontogeny of rat anterior pituita ry GABA(B) receptors and the pattern of subunit expression in rats of both sexes were determined. Western blot analysis showed a temporal decrease in GABA(B) subunits GABA(B(1a)) and GABA(B(1b)) expression in female anterior pituitary membranes from day 4 to adulthood, with GABA(B(1a)) being signifi cantly more abundant than GABA(B(1b)) at early stages of development; the G ABA(B(2)) subunit was barely detectable. In the male, GABA(B(1a)) followed a similar pattern and appeared to be significantly less abundant than in 4- and 12-day-old females; GABA(B(1b)) and GABA(B(2)) expression in the male was barely detectable. Scatchard plot analysis showed a temporal decrease i n binding sites in female anterior pituitary membranes, in agreement with t he western blot results. The number of binding sites was significantly high er in female than in male 4-day-old membranes. Dissociation constant values were similar for both sexes at all ages studied. This study reports for the first time the ontogeny of anterior pituitary GA BA(B) receptors, showing a particular developmental pattern of subunit expr ession and a clear sexual dimorphism. (C) 2000 Elsevier Science Ltd. All ri ghts reserved.