Effect of GABA on the acrosome reaction. Sperm were treated with GABA and GABA antagonists. GABA administration enhanced the acrosome reaction (A). Mouse sperm were capacitated in HTF
medium for 90 min. Saline or various concentrations of GABA (0.1, 1, 10, and 100 µM) dissolved in saline were added to equivalent aliquots of the suspension (100 µl: 5 × 106
cells/ml) and cultured for 30 min. (B) The effect of bicuculline, a GABA A receptor-specific antagonist. A sperm suspension was cultured with bicuculline dissolved in DMSO in the
presence of saline or GABA (1 µM). All the groups contained 0.1% DMSO. Sperm acrosomal disappearance rates were evaluated by calculating the number of PNA-negative sperm among total
sperm. Each experiment was replicated at least three times. Data are shown as the means ± SE (* P < 0.05, ** P < 0.01).