Subunit composition and function of GABA(A) receptors of rat spermatozoa

GABA triggers mammalian sperm acrosome reaction (AR). Here, evidence is presented, showing that rat spermatozoa contain GABA(A) receptors, composed of alpha(5), beta(1), and beta(3) subunits. The effects of GABA(A) receptor agonist and antagonist on the induction of AR in rat spermatozoa were assessed using the chlortetracycline assay. Muscimol, a GABA(A) receptor agonist, triggered AR; whereas bicuculline, a GABA(A) receptor antagonist and picrotoxin, a GABA(A) receptor/Cl- channel blocker, inhibited the ability of GAGA or progesterone to induce AR. In conclusion, GABA(A) receptors appear to mediate the action of progesterone in inducing AR in rat spermatozoa.