Generation of the endocochlear potential: a biophysical model.

The generation and maintenance of the endocochlear potential (EP) by the stria vascularis is essential for proper function of the cochlea. We present a mathematical model that captures the critical biophysical interactions between the distinct cellular layers that generate the EP. By describing the relationship between the K(+) concentration in the intrastrial space and the intermediate cell transmembrane potential, we rationalize the presence of a large intermediate cell K(+) conductance and predict that the intrastrial [K(+)] is approximately 4 mM at steady state. The model also predicts that the stria vascularis is capable of buffering the EP against external perturbations in a manner modulated by changes in intrastrial [K(+)], thus facilitating hearing sensitivity across the broad dynamic range of the auditory system.