Postnatal developmental changes in the medial nucleus of the trapezoid body in a mouse model of auditory pathology.

Age-related hearing loss (AHL) is a multifactorial disorder characterized by a decline in peripheral and central auditory function. Here, we examined synaptic transmission in DBA/2 mice, which carry the AHL8 gene, at the identifiable glutamatergic synapse in the medial nucleus of the trapezoid body (MNTB), a nucleus in the superior olivary complex critical for acoustic timing. Mice exhibited raised auditory brainstem thresholds by P14, soon after hearing onset. Excitatory postsynaptic currents were prolonged; however, postsynaptic excitability was normal. By P18, high-frequency hearing loss was evident. Coincident with the onset of hearing loss, MNTB principal neurons displayed changes in intrinsic firing properties. These results suggest that changes in transmission in the superior olivary complex are associated with early onset hearing loss.