Properties of the olivocochlear efferent synapse relevant for the regulation of the auditory periphery

LUCAS G. VATTINO; A. BELÉN ELGOYHEN; ELEONORA KATZ

Congreso; XXIX Annual Meeting of the Argentine Society for Research in Neuroscience (SAN); 2014

Sociedad Argentina de investigación en Neurociencias

In mammals, the auditory sensory epithelium contains two types of mechanotransducer cells, inner and outer hair cells (IHCs and OHCs, respectively). IHCs are involved in conveying acoustic stimuli to the central nervous system while OHCs are implicated in sound amplification. OHC and IHC activity (IHC only transiently during development) is modulated by the medial olivocochlear system (MOC). The synapse between the MOC fibers and cochlear hair cells is cholinergic, fast and inhibitory. Inhibition is brought about by Ca2+ entry through the α9α10 nicotinic cholinergic receptor (nAChR) and the subsequent activation of Ca2+-sensitive K+ channels of the SK2 type. At the MOC-IHC synapse, ACh release is supported by P/Q- and N-type voltage-gated Ca2+ channels (VGCC) whereas those mediating release at the MOC-OHC synapse remain unknown. In previous work, performed in apical cochlear explants, we showed that the strength of the MOC-OHC synapse increases upon high frequency stimulation due to summation and facilitation. Recent studies suggest that in the basal region, where high frequency sounds are decoded, the cholinergic response is mediated by the α9α10 nAChR coupled to BK channels. As the kinetics of BK and SK2 channels are different, the short term plasticity (STP) properties of this synapse may also vary. We aim at elucidating, by electrophysiological methods, the VGCC mediating release at the MOC-OHC synapse and its STP properties along the tonotopic axis of the cochlea.