INGEBI   02650
INSTITUTO DE INVESTIGACIONES EN INGENIERIA GENETICA Y BIOLOGIA MOLECULAR "DR. HECTOR N TORRES"
Unidad Ejecutora - UE
congresos y reuniones científicas
Título:
Short term facilitation at the Inner Hair Cell ribbon synapse
Autor/es:
JUAN D. GOUTMAN; ELISABETH GLOWATZKI
Lugar:
Biddeford, Maine
Reunión:
Conferencia; Gordon Research Conference on Synaptic Transmission; 2010
Institución organizadora:
Gordon Research Conferences
Resumen:
In the mammalian cochlea, inner hair cells (IHC) are responsible for the detection and transduction of sound signals into electrical potentials. This information is then transmitted to the brain through its afferent synapse. In order to code for fast and transient acoustic signals, this synapse requires high efficiency and temporal precision. Simultaneous whole cell patch clamp recordings where performed from IHCs and contacting afferent dendrites in excised organs of Corti from neonatal rats. The afferent synaptic response was studied while manipulating IHC membrane potential and calcium influx. We have previously characterized the voltage dependence of release. In response to long (1 s) IHC depolarizations, the afferent fiber response showed synaptic depression. When IHCs were depolarized from a holding potential of -89 mV to -29 mV for only 2 ms, a high failure rate for release was found. Successful responses were small in amplitude and showed long synaptic delays (3-4 ms). If a conditioning step to an intermediate potential (~-60 mV) was applied to the IHC before the test pulse, a significant increase in the probability of release was observed. Additionally, the delay of the response was shorter (~1 ms). Similar results were found when conditioning was induced with a paired pulse protocol. These results suggest that release at the IHC ribbon synapse can be modulated by the presynaptic membrane potential resembling facilitation in the CNS. IHC physiological resting potential (~-60 mV) allows for synaptic activity in the absence of any sound stimulation and, as we show here, may generate a steady facilitated regime. This might be a mechanism by which precision of exocytosis at this synapse is improved.