Subunit Composition and Function of GABAA 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 ₅, ₁ and 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 GABA or progesterone to induce AR. In conclusion, GABA_A receptors appear to mediate the action of progesterone in inducing AR in rat spermatozoa.