Functional development of the medial olivocochlear efferent innervation before the onset of hearing

JAVIER ZORRILLA DE SAN MARTÍN; JIMENA BALLESTERO; ANA BELÉN ELGOYHEN; ELEONORA KATZ

San Diego

Congreso; 35th Midwinter Meeting of the Association for Research in Otolaryngology; 2012

Association for Research in Otolaryngology

Before the onset of hearing (postnatal day (P)12 in mice), inner hair cells (IHCs) are transiently innervated by medial olivocochlear (MOC) fibres. At P9-11 transmitter release 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. We have previously shown that the quantal content (m) of transmitter release significantly increased between P5-7 and P9-11 (0.5 and 1.7, respectively) and that this increment was 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. At P5-7, 0mega-Agatoxin IVA reduced m to 37±6% of control (p