Expression of the GABAA receptor/chloride channel in murine spermatogenic cells.

Previous studies from our laboratory have demonstrated that γ-aminobutyric acid (GABA) and GABAB receptor subunits are expressed within the acrosome of spermatids during spermiogenesis. Furthermore, our previous study with the glutamate decarboxylase (GAD) 67-GFP knock-in mouse demonstrated that GFP-positive cells were localized to the epithelium of the caput of epididymis. In the present study, we detected GABAA subunits, including α1, α5, β1-3 and γ3, and both isoforms of GAD, GAD65 and GAD67, in mouse spermatogenic cells using RT-PCR. The expression of these proteins was subsequently confirmed by western blot analysis. Immunohistochemistry also revealed that GABA, GAD65, and α5, β1 and γ3 subunits of the GABAA receptor were localized in the membrane of spermatogenic cells, including spermatocytes and spermatids. The whole-cell patch-clamp analysis demonstrated that GABA application induced an inward chloride current in some of the large and round spermatogenic cells. Our findings show that spermatogenic cells have a GABA producing system by themselves, and that GABA may function via the ionotropic GABAA receptor. This data suggests that the GABAergic system may play important roles in the male reproductive system.