Same location of the source of P1 of BAEPs and N1 of CAP in guinea pig.

The purpose of this study was to point out the location of N1 and N2 of the compound action potential (CAP) and the first waves of the brainstem auditory evoked potentials (BAEPs) by the mean of the section of the eighth nerve at the porus acousticus in guinea pigs. Our results agree with most of the studies in the literature. In the absence of lesion of the internal auditory artery, the section of the cochlear nerve induced the persistence, alone, of the P1 of BAEPs in which latency was similar to initial P1 before section, and the subsequent waves disappeared. Simultaneously, a monophasic negative potential (N1) of the auditory nerve remained without N2. When the section included the internal auditory artery all BAEPs and CAP components disappeared simultaneously and very suddenly just after the section. These results definitively excluded a proximal contribution of the cochlear nerve in the N1 of CAP and P1 of BAEPs. The N2 of CAP and P2 of BAEPs are not generated, even in part, in the intracochlear or intrapetrous portion of the cochlear nerve.