Short-term synaptic plasticity at the medial olivocochlear hair cell synapse in ¦Á9L9¨ªT knock-in

BALLESTERO J; ALVAREZ HEDU¨¢N F; FUCHS PA; KATZ E; ELGOYHEN AB

Congreso; XXVII Congreso Anual de la Sociedad Argentina de Investigaci¨®n en Neurociencia; 2011

Cochlear amplification is regulated by medial olivocochlear (MOC) neurons that synapse onto outer hair cells (OHCs). This synapse is mediated by the ¦Á9¦Á10 nicotinic receptor (nAChRs). We have generated a mouse with a point mutation (L9¡¯T) in the ¦Á9¦Á10 nAChR that produces longer-lasting inhibitory postsynaptic currents (IPSCs) and changes the magnitude and the dynamics of the efferent-mediated inhibition of cochlear responses (Taranda et al. Plos Biology, 2009). Our goal is now to determine if there is a consequent change in the short-term plasticity (STP) properties of the MOC-hair cell synapse. Synaptic activity was recorded in voltage-clamped inner hair cells (IHCs) from excised apical turns of wild-type (wt) or ¦Á9L9¡¯T knock-in (kin) mouse cochleas (P9-11), during electrical stimulation of the MOC fibers. Electrically evoked IPSCs in kin mice had longer decay times and smaller amplitudes. Prolonged high frequency stimulation produced an initial increase in the postsynaptic response, followed by depression. In wt IHCs, peak responses were reached in the 1st second and then rapidly decayed by ~80%. In kin mice, peak responses were reached after ̴3 sec of stimulation and then slowly decayed by 50% at end of the train. These results show that changes in the dynamics of the MOC-hair cell synapse induce dramatic changes in its STP properties.