MN and Elgoyhen AB. The efferent olivocochlear system modulates the tonotopy of a central auditory nuclei

DI GUILMI, MN AND ELGOYHEN AB

Bahia Blanca

Congreso; Reunión anual (XLIII) de La Sociedad Argentina de Biofísica; 2014

Sociedad Argentina de Biofísica

The auditory system in many mammals is immature at birth but precisely organized in adults. Spontaneous activity in the inner ear, comes into play to guide this process. The rate of this spontaneous activity is under the control of an efferent pathway that descends from the brain. In the medial nucleus of the trapezoid body (MNTB), neurons are topographically organized along a medio-lateral axis with the most medially located cells responding to high frequencies, changing to lower characteristic frequencies in the most lateral cells. Previous studies provided evidence that HCN channels are topographically arranged in the MNTB (Leao et. al., 2006). The specific aim of this project is to understand the role of the olivocochlear efferent system in the correct establishment of auditory circuits. For this propose, we studied the tonotopy on the MNTB in a mouse model with an enhanced efferent functionality (Chrna9L9´T, KI). Under voltage-clamp mode, Ih currents were larger in medial than lateral cells in WT. However, this tonotopic deference is reduced in the KI where lateral cells showed the same large current amplitudes than medial ones. Current-clamp experiments support these observations where a larger voltage sag in response to hyperpolarizing currents was observed in medial than lateral cells in WT without changes in the KI. Our ongoing data suggest that the efferent pathway could be involved in the refinement of the tonotopic map ensuring the presence of high frequency coding cells.Leao, et al. J Physiol 571 (2006) 563.