Project 5

Purinergic regulation of the endocochlear potential.

The steady voltage in scala media is a key factor in determining hearing sensitivity and spontaneous firing of auditory neurons. Disturbances of this voltage could underly a variety of hearing pathologies including tinnitus and hence it is interesting to study the mechanism by which it is regulated. We have found consistently that perfusion of the cochlea with agonists of P2 receptors causes a marked rise in the voltage in the scala media (endocochlear potential). Threepossible hypotheses ofthe mechanism of this increase are 1) that there is a change in activity in an efferent feedback loop regulating the voltage,2) that there is activation of P2 receptors in the stria vascularis (the transporting epithelium that is responsible for generating the voltage) and 3) there is a reduction in the current drain on the scala media voltage by closure of ion channels. These hypotheses will be tested by intracochlear perfusion and intracochlear electrical measurements.