Acrosome reaction in the epididymal sperm of Chinchilla lanigera. Effect of progesterone, A23187 and stimulation of a GABAA-like receptor.

Little is known about the reproductive biology of Chinchilla lanigera in captivity. Currently there are no parameters to evaluate the quality of the semen of males that are sold as breeding stock, so they are selected according to their phenotypic characteristics, which cannot guarantee their reproductive efficiency. We worked with sexually mature males; the sperm were collected from the cauda epididymis by puncture. Capacitated sperm were incubated at 37 °C with different concentrations of progesterone. The results showed a biphasic behavior, where the increase in the percentage of the acrosome reaction (AR) was significant between 2.5-5 μM, and a maximum response with a dose of 20 μM. Also the suspension of sperm incubated with different concentrations of ionophore A23187 inducing response is obtained with a concentration of 10 μM. Stimulation of the Gamma-aminobutyric acid (GABA)A -like receptor by treating the sperm with different concentrations of muscimol, a specific receptor agonist, also induce acrosome reaction. The dose-response curve showed a biphasic effect with a maximum response at a concentration of 2.5 μM. The pretreatment of sperm suspension with a specific receptor antagonist, picrotoxin, a decrease was observed in the percentage of reacted perm. These studies represent a first step towards the establishment of standard parameters to determine the functionality and fertilizing capacity of Chinchilla sperm. In addition, our results indicate that the Chinchilla spermatozoa can undergo the AR when treated with A23187 or progesterone at high percentages. It also shows a clear involvement of GABAA -like receptors in acrosome exocytosis in sperm obtained by epididymal cauda.