Purinergic modulation of synaptic activity at the efferent synapse in mice inner ear

FACUNDO ALVAREZ HEDUAN; KATZ, E.; GOUTMAN JD; ELGOYHEN, AB.

Mar del Plata

Congreso; XXX Congreso Anual de la Sociedad Argentina de Investigación en Neurociencias (SAN); 2015

Sociedad Argentina de Investigación en Neurociencias (SAN)

The inner ear receives innervation from efferent cholinergic fibers, descending directly from the medial olivary complex (MOC) in the auditory brainstem. Acetylcholine (ACh) released by these fibers produces synaptic inhibition by means of a nicotinic receptor with high Ca2+ permeability coupled to a Ca2+-activated potassium channel. MOC fibers directly innervate outer hair cells (OHC), controlling the amplification capability of these cells in the mature cochlea. However, during the first two postnatal weeks, MOC fibers innervate inner hair cells (IHC), controlling an intrinsic electrical activity of these cells. This activity is driven and/or modulated by ATP released from cochlear supporting cells. Here, we investigated the interaction between ATP and MOC inhibition to hair cells. By recording inhibitory post synaptic currents (IPSC) in P9-11 mice, we showed that ATP decreases ACh release through the activation of presynaptic P2Y receptors. In this work, we evaluated this effect across development (P5-7) and found that ATP-induced inhibition is even stronger at this stage. Finally, because ATP-mediated signaling has been proposed as a mechanism of sensing damage in the cochlea, we studied if ATP modulates the MOC-OHC synapse. We found that ATP decreases IPSC amplitudes in P11-13 mice. This effect was abolished by the non-specific P2 antagonist, suramin. Our findings show an inhibitory role of ATP at the efferent synapse both during development and after the onset of hearing.