Calcium is an important second messenger in sperma tozoa of various species including mammals and is required for acrosomal e ocytosis. In the present stu dies, incubation of the capacitated human sperm with SIZP resulted in transient calcium peak. VOCCs are important mediators of early intracellular calcium influ which are activated on membrane potential changes following Belinostat HDAC agonist binding. In this manuscript, we have identified type of VOCCs responsible for the early intra cellular calcium influ as well as their role in acrosomal e ocytosis mediated by SIZP in human sperm. Prior treatment with T type VOCC inhibitor, Pimozide abol ished the early i peak whereas L type inhibitor Verapamil failed to do so. Role of T type VOCCs was further reinforced by inhibition of acrosome reaction mediated by human SIZP in presence of two different T type VOCCs inhibitors.

Further, chelating the e tracellular calcium by EGTA also led to inhibition of SIZP mediated acrosome reac tion. In contrast to T type VOCCs inhibitors, L type VOCCs inhibitors failed to inhibit SIZP mediated acrosome reaction. Patrat et al, has shown that solubilized zona prepared from unfertilized and fertilized human eggs induces acrosome reaction and increase in i is mediated by T type VOCC. However, the ability of SIZP prepared from fer tilized eggs to induce acrosome reaction needs further investigation. Besides, being an important inhibitory neurotransmit ter in the central nervous system, g Aminobutyric acid also operates in the human genital tract. g ami nobutyric acid receptors and the GABA uptake system are present in both male and female genital tract.

A spe cific binding and transport system is present on the plasma membrane of the human spermatozoon. GABA also induces acrosome reaction in human sperm. Out of two classified GABA receptor subtypes GABAA and GABAB, GABAA receptor is a plasma GSK-3 membrane multi subunit receptor comple linked to the chloride channel whose activation results in the opening of the chloride Tofacitinib citrate channel. Progesterone and its metabolites potentiate the effects of GABA on this receptor. Picroto in a GABAA receptor inhibitor, inhibits pro gesterone as well as recombinant human ZP3 fragment mediated acrosome reaction. Studies presented in this manuscript suggest that in humans, ZP mediated induction of acrosome reaction is also inhibited by inhibitor of GABAA receptor. Heat solubilized human ZP mediated acrosome reac tion involves activation of Gi protein coupled receptor pathway which is in concordance with previous reports.