Properties of the olivocochlear-outer hair cell synapse in the mouse cochlea.

JIMENA A. BALLESTERO; JAVIER ZORRILLA DE SAN MARTÍN; JUAN D. GOUTMAN; PAUL A. FUCHS; ANA BELÉN ELGOYHEN; ELEONORA KATZ

Huerta Grande, Córdoba, Argentina

Congreso; Second Joint Meeting of the Argentine Society for Neurosciences (SAN) and the Argentine Workshop in Neurosciences (TAN) (IIRCN); 2010

Sociedad Argentina de Investigaciones en Neurociencias (SAN) y el Taller Argentino de Neurociencias (TAN)

In the Organ of Corti, the sensory epithelia of the mammalian auditory system, inner hair cells transduce sound stimuli while outer hair cells (OHCs) participate in the amplification of sound. OHC function is inhibited by efferent cholinergic olivocochlear (OC) fibers. OC fibers firing rate varies according to the type and intensity of sound. In turn, the degree of inhibition exerted by OC fibers on the auditory function changes with firing rates. In this work we study the properties of the OC synapse onto OHCs. Synaptic activity was recorded in voltage-clamped OHCs from the apical turn of the mouse cochlea (P10-12) during electrical stimulation of OC fibers. Activation of fibers by single shocks evoked inhibitory postsynaptic currents with a low rate of success. Paired-pulse protocols showed that this synapse facilitates with maximum efficacy at 10 ms pulse intervals. Trains of stimulation at different frequencies produced increasing levels of transmitter release proportional to the stimulus frequency due both to summation and facilitation of synaptic responses. These results show that this synapse facilitates at physiological OC fibers firing frequencies. This property could be relevant for encoding different degrees of OC inhibition in response to variable sound stimulation.