Neurosteroid synthesis-mediated regulation of GABA(A) receptors: relevance to the ovarian cycle and stress. Maguire J, Mody I J Neurosci. 2007 Feb 28;27(9):2155-62. Progesterone (5 mg/kg, twice daily) upregulates the expression of GABA(A)R delta subunits and enhances the tonic inhibition mediated by these receptors in dentate gyrus granule cells (DGGCs). These changes in males as well as ovarian cycle-induced changes in females can be blocked by finasteride, an antagonist of neurosteroid synthesis from progesterone.