Synaptic strength and plasticity at the medial olivocochlear-inner hair cell synapse is not altered in mice lacking functional BK channels

GRACIELA KEARNEY; LUCAS VATTINO; CAROLINA WEDEMEYER; ANDREA MEREDITH; SONJA PYOTT; PAUL FUCHS; ANA BELEN ELGOYHEN; ELEONORA KATZ

Buenos Aires

Congreso; 2nd Congress of the Federation of Latin-American and Caribbean Societies for Neuroscience (FALAN).; 2016

Before the onset of hearing (postnatal day (P)12 in mice), cochlear inner hair cells (IHCs) present spontaneous calcium action potentials that trigger glutamate release. Also, from birth until P12, IHCs are innervated by medial olivocochlear (MOC) fibers postulated to regulate IHC spike frequency. ACh release from MOC terminals at P9-11 is mediated by N- and P/Q-type voltage-gated Ca2+ channels (VGCCs) while L-type VGCCs coupled to BK channels exert a strong negative control on synaptic strength (Zorrilla de San Martin et al., 2010).To probe the role of BK channels in efferent synaptic function, we isolated cochleas from BK channel knockout mice and their wild-type littermates (Slo-/-, Slo+/+) at P9-11 and measured evoked release during whole-cell voltage-clamp recordings from IHCs. We found no significant differences between genotypes in quantum content (Slo+/+ 0.69±0.17, Slo-/- 0.69±0.14, p=0.97; n=10) or short-term plasticity upon high frequency stimulation. Interestingly, an L-type VGCC agonist (BayK) increased quantum content only in Slo-/- mice (control 0.91±0.37, 10 uM Bay-K 1.60±0.11, p