Functional changes in synaptic transmission at the mouse medial olivocochlear (MOC)-inner hair cell synapse during neonatal development

GRACIELA KEARNEY; LUCAS VATTINO; CAROLINA WEDEMEYER; JAVIER ZORRILLA DE SAN MARTIN; ANA BELEN ELGOYHEN; ELEONORA KATZ

Mar del Plata

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

Sociedad Argentina de Neurociencias

Inner hair cells (IHC) are innervated by MOC fibers since birth to the onset of hearing (postnatal day 12, P12). At P9-11 ACh release is supported by P/Q- and N-type VGCC and negatively regulated by L-type VGCC coupled to BK channels. The transient nature of the MOC-IHC synapse suggests there might be changes in the properties of synaptic transmission throughout this period. Short term synaptic plasticity (STP) is the change in synaptic strength (facilitation/depression) as a consequence of preceding activity. We have shown that stimulation trains at 10, 40 and 100 Hz led to depression at P9-11 whereas at P6-7 the 10 Hz train led to facilitation and the 40 and 100 Hz trains to facilitation followed by depression. We now found that at P4 synapses trains at 10, 40 and 100 Hz caused a 1.5±0.7; 2.2±0.6 and 2.0±0.6-fold increase, respectively, in the ratio between the amplitude of the tenth and the first evoked synaptic current, indicating that at this stage there is facilitation even at the highest frequencies tested. Consistently, both the quantal content (0.3±0.1 P4; 0.8±0.1 P6-7; 1.6±0.2 P9-11 p