INGEBI   02650
INSTITUTO DE INVESTIGACIONES EN INGENIERIA GENETICA Y BIOLOGIA MOLECULAR "DR. HECTOR N TORRES"
Unidad Ejecutora - UE
congresos y reuniones científicas
Título:
Properties of the olivocochlear-outer hair cell synapse in the mouse cochlea
Autor/es:
BALLESTERO J; ZORRILA DE SAN MARTIN J; FUCHS P; ELGOYHEN AB; KATZ E
Lugar:
Anaheim, California, USA
Reunión:
Congreso; 33rd Midwinter Meeting of the Association for Research in Otolaryngology; 2010
Institución organizadora:
ARO
Resumen:
<!-- /* Style Definitions */ p.MsoNormal, li.MsoNormal, div.MsoNormal {mso-style-parent:""; margin:0cm; margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:12.0pt; font-family:"Times New Roman"; mso-fareast-font-family:"Times New Roman";} @page Section1 {size:612.0pt 792.0pt; margin:70.85pt 3.0cm 70.85pt 3.0cm; mso-header-margin:36.0pt; mso-footer-margin:36.0pt; mso-paper-source:0;} div.Section1 {page:Section1;} --> In the adult cochlea, the function of outer hair cells (OHCs) is modulated by efferent cholinergic olivocochlear (OC) fibers projecting from the central nervous system.  It has been previously shown that the firing rate of OC fibers varies according to the type of sound stimulation (noise, tones, monoaural, binaural, etc.) and that it increases with sound intensity (Brown et al., 1998). These changes in firing rates would presumably cause different strengths in the feedback effect exerted by the OC system. In the present work we used the technique developed by Goutman et al., (2005) to study the properties of the OC synapse onto OHCs.  Briefly, synaptic activity was recorded in voltage-clamped OHCs from an excised apical turn of the mouse cochlea (10-12 postnatal days) during stimulation of OC fibers with a bipolar electrode placed in the modiolar region. Activation of efferent terminals by single shocks evoked inhibitory postsynaptic currents (IPSCs) with a very low rate of success (quantal content: 0.14 ± 0.03, n = 30 cells). Paired-pulse protocols showed that this synapse facilitates with maximum efficacy at pulse intervals of 10 ms (facilitation index = 2.1 ± 0.4; n = 8). Accordingly, trains of stimuli at different frequencies (10-100 Hz) produced increasing levels of transmitter release. This phenomenon, together with summation of synaptic currents, resulted in an increase of OHC responses proportional to the stimulus frequency (normalized IPSC amplitude Imax/Isingle-shock:  5.4 ± 1.0; 8.5 ± 3.7; 12.3 ± 0.8; 15.6 ± 1.0 for 25, 50, 60 and 80 Hz, respectively; n = 2-4).  These results show that this synapse can facilitate at intervals that correlate with the physiological frequencies at which OC fibers fire. This property could be relevant for encoding different degrees of OC fiber activity in response to variable sound stimulation.