Voltage oscillations in mammalian metaphase II oocytes.

The membrane potential has been measured in ovulated mouse oocytes using conventional electrophysiological techniques. Temporal oscillations in membrane voltage have been observed in the oocytes, with periods of about 6 h. This oscillatory pattern, peculiar to oocytes in metaphase II, might explain the differences in membrane potential values reported in several studies on mammalian oocytes.