Developmental changes in the ion channels that support transmitter release at the transient efferent-inner hair cell synapse in the mouse cochlea.

GRACIELA KEARNEY; JAVIER ZORRILLA DE SAN MARTÍN; CAROLINA WEDEMEYER; ANA B ELGOYHEN; ELEONORA KATZ

Huerta Grande, Córdoba

Congreso; XXVIII Congreso Anual de la Sociedad Argentina de Investigación en Neurociencias (SAN); 2013

Sociedad Argentina de Investigación en Neurociencias

During postnatal development, cochlear inner hair cells (IHCs) are transiently innervated by medial olivocochlear (MOC) fibres. This innervation is functional since birth, postnatal (P) 0 until the onset of hearing (P12 in rats and mice). This synapse is cholinergic, fast and inhibitory. At P9-11 the release of acetylcholine (ACh) is supported by both P/Q and N-type voltage-gated Ca2+ channels (VGCC) and negatively regulated by L-type VGCC, coupled to the activation of BK channels. The quantal content (m) of transmitter release significantly increases between P5-7 and P9-11 (0.5 and 1.7, respectively) and this increment is accompanied by dramatic changes in the short term plasticity (STP) properties of this synapse. Our goal is now to determine the basis for these developmental changes in synaptic transmission. Postsynaptic responses were monitored in whole-cell voltage-clamped IHCs while electrically stimulating the efferent fibres in isolated mouse organs of Corti. We have previously reported that at P5-7, omega-Agatoxin IVA reduced m to 37±6% of control (p