Our previous studies showed that γ-aminobutyric acid (GABA)A and GABAB receptors are involved in rat sperm acrosome reaction induced by progesterone or GABA. Here,we report the presence of GABAc receptor in rat testis and spermatozoa.Full-length complementary DNA encoding the ρ1，ρ2 and ρ3 subunits of GABAc receptor were cloned from rat testis;their sequences are identical to those of rat GABAc receptor in retina.Reverse transcription-polymerase chain reaction analysis showed that during the development of rat testis,the transcript levels of the ρ1 and ρ2 subunits showed little change,while the expression of ρ3 was gradually up-regulated.Immunofluorescence analysis using an anti-ρ1 antibody revealed that GABAc receptor exists on the elongated spermatid and sperm.Using a chlortetracycline assay,we found that N(4)-chloroacetylcytosine arabinoside, a GABAc receptor agonist,triggered rat sperm acrosome reaction;whereas(1,2,5,6-tetrahydropyridin-4-yl)methylphosphinic acid,a GABAc receptor antagonist, inhibited the ability of N(4)-chloroacetylcytosine arabinoside to induce acrosome reaction.These results suggested that GABAc receptors are also involved in rat sperm acrosome reaction.
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