Rabbit oocyte maturation: changes of membrane resistance, capacitance, and the frequency of spontaneous transient...

Immature oocytes from rabbits were examined with electrophysiological techniques to determine if their membrane properties change during maturation. The input resistance increased and input capacitance decreased during maturation, although no significant change in membrane potential was observed. The changes observed were consistent with a decrease of corona radiata-oocyte electrical coupling accompanying maturation. Spontaneous transient depolarizations were recorded from immature oocytes surrounded by corona radiata, but not from mature ova. Each event consisted of a rapid depolarization, sustained for 1-100 sec, and a slow repolarization to the resting potential. Spontaneous inward currents with a time course similar to the spontaneous transient depolarizations occurred when the oocyte's membrane potential was held constant by voltage clamp. The frequency with which spontaneous transient depolarizations occurred decreased during maturation. These findings are consistent with a model in which spontaneous depolarizations originate in corona radiata cells and are detected in the oocyte via electrical coupling.