INGEBI   02650
INSTITUTO DE INVESTIGACIONES EN INGENIERIA GENETICA Y BIOLOGIA MOLECULAR "DR. HECTOR N TORRES"
Unidad Ejecutora - UE
congresos y reuniones científicas
Título:
Development of short term plasticity properties at the transient medial olivocochlear-inner hair cell (MOC-IHC) synapse.
Autor/es:
JAVIER ZORRILLA DE SAN MARTÍN; JIMENA BALLESTERO; PAUL A FUCHS; ANA BELÉN ELGOYHEN; ELEONORA KATZ
Lugar:
Marsella, Francia
Reunión:
Workshop; 10e Colloque Societé des Neurosciences; 2011
Institución organizadora:
Sociedad Francesa de Neurociencias
Resumen:
From birth until the onset of hearing (postnatal day (P) 12), IHCs
are transiently innervated by cholinergic medial olivocochlear (MOC) fibers. At
this synapse, transmitter release is supported by both N- and P/Q-type
voltage-gated calcium channels (VGCCs) (Zorrilla de San Martín et al., J.
Neurosci 2010). The fast formation and retraction of the MOC-IHC synapse
suggest there may also be associated changes in synaptic transmission throughout this period. Short term plasticity (STP) is a dynamic process
that depends on the balance between facilitation and depression of synaptic
responses caused by preceding activity. Our goal is to determine whether there are changes in STP at the MOC-IHC synapse during
development and, if so, to understand the mechanisms underlying them. Synaptic
activity was recorded in voltage-clamped IHCs from excised apical turns of the mouse
cochlea at two developmental stages (P5-7 and P9-11) during electrical
stimulation of the MOC fibers. Ten-pulse trains at 10, 20, 40 and 100 Hz
applied to P5-7 MOC-IHC synapses led to 1.8±0.3; 1.7±0.2; 1.8±0.3 and 2±0.4-fold
increase in synaptic efficacy, respectively, estimated as the ratio between the
mean amplitude of the fifth and the first evoked synaptic current (S5/S1);
n=7-10. The same protocols applied to P9-11 synapses led to a progressive
decrease of the S5/S1 value (0.8±0.1; 0.7±0.1; 0.6±0.1;
0.4±0.1 for the 10, 20, 40 and 100 Hz trains, respectively; n=12-18).
Depression upon high frequency stimulation at P9-11 was reversed to
facilitation when reducing quantal output either by decreasing [Ca2+]o
or by blocking P/Q-type VGCCs with w-Agatoxin
IVA (200 nM). Our results show there is a developmental switch from
facilitation to depression upon high frequency stimulation consistent with the
increment in the probability of release. We are now studying whether these
changes in synaptic transmission can be accounted for by differences in the
coupling between calcium influx and transmitter release.