Hormone-dependent regulation of GABAA receptor γ subunit mRNAs in sexually dimorphic regions of the rat brain

Abstract

Transmission mediated by gamma–aminobutyric acid type A (GABA_A) receptors expressed within the medial preoptic area (mPOA) and the ventromedial nucleus (VMN) of the hypothalamus is known to play critical, but contrasting, roles in regulating steroid–dependent sexual behaviours in rats. Previous studies have demonstrated a striking dichotomy in receptor composition between the two regions with regard to α, but not α or β, subunit expression. To test if gonadal steroids regulate the expression of the γ subunit genes within the mPOA and the VMN, in situ hybridization analysis for messenger RNAs encoding the γ1, γ2Short (γ2S) and γ2Long (γ2L) subunits was done in gonadectomized male and female rats and in gonadally intact females over the oestrous cycle. No significant differences in the expression of the γ subunit mRNAs were observed in gonadectomized male versus female rats. Significant effects of gonadal state in female rats were observed for γ1 mRNA levels in the mPOA and γ2L levels in the VMN. These data demonstrate that gonadal hormones exert activational control of expression of GABAA receptor γ subunit mRNAs and suggest that differences in receptor structure may contribute to the functional modulation of female sexual behaviours mediated by GABAergic transmission in these regions.