The Xenopus Oocyte
The Xenopus laevis oocyte is a commonly used cell for electrophysiological recordings. They're a popular model because of their large size (~ 1.0 mm) which makes their handling and manipulation easy. This makes them attractive as models for electrophysiology.
Oocytes are precursors to mature egg cells and are stored in the ovarian lobes of the adult female frog. They're classified in stages (from stage I to stage VI) depending their developmental state. Stage V and VI oocytes are used for electrophysiological experiments and are harvested by survival surgery or after euthanization of the frog.
Oocytes have two poles, the animal pole and the vegital pole (as seen in the picture above). The animal pole is dark brown in color and the vegital pole is yellow.
Oocytes are surrounded by a layer of follicle cells that can be left intact or removed (either manually or by treatment with collagenase). The oocyte is electrically coupled to the follicle cells by gap junctions, so that electrical events in the follicle cells can be measured by recording from the oocyte membrane.
The resting oocyte (with follicle cells intact) maintains a membrane potential of -50 to -60 mV, mainly due to K+ leak out of the cell. Since K+ is the most permeable ion, the resting membrane potential is closest to its equilibrium potential.
Back to Oocyte Main page