α-Aminobutyric Acid Receptors in Anterior Pituitary and Brain Areas after Median Eminence Lesions*

Previous results have indicated that the median eminence (ME) plays a key role in the regulation of estrogen and dopamine receptors in the anterior pituitary (AP). Since 3H-labeled γ-aminobutyric acid ([3H]GABA) receptors have been described in the pituitary as well as in the brain, the aim of the present work was to investigate whether those receptors are also under hypothalamic control. Ovariectomized adults rats were divided into two groups. In the first one, the ME was lesioned by an anodic current (MEL); the second group consisted of shamoperated controls. Animals were used 7–14 days thereafter to study [3H]GABA binding in a crude mitochondrial membrane fraction prepared from the anterior pituitary, the hypothalamicpreoptic suprachiasmatic area, or the frontoparietal cortex. Binding of [3H]GABA was a saturable process, with high affinity in all studied structures. In AP, Scatchard analysis of the saturation curves indicated similar Kd values in sham and MEL rats; the maximal number of binding sites i...