INGEBI   02650
INSTITUTO DE INVESTIGACIONES EN INGENIERIA GENETICA Y BIOLOGIA MOLECULAR "DR. HECTOR N TORRES"
Unidad Ejecutora - UE
artículos
Título:
Presynaptic facilitation is required for efferent control of the auditory periphery
Autor/es:
JIMENA BALLESTERO; JAVIER ZORRILLA DE SAN MARTÍN; JUAN GOUTMAN; ANA BELÉN ELGOYHEN; PAUL A. FUCHS; ELEONORA KATZ
Revista:
JOURNAL OF NEUROSCIENCE
Editorial:
SOC NEUROSCIENCE
Referencias:
Año: 2011 vol. 31 p. 14763 - 14774
ISSN:
0270-6474
Resumen:
In the mammalian inner ear, the gain control of
auditory inputs is exerted by medial olivocochlear (MOC) neurons that innervate
cochlear outer hair cells (OHCs). OHCs mechanically amplify the incoming sound
waves by virtue of their electromotile properties while the MOC system reduces
the gain of auditory inputs by inhibiting OHCs function. How this process is orchestrated
at the synaptic level remains unknown. In the present study, MOC firing was
evoked by electrical stimulation in an isolated mouse cochlear preparation,
while OHCs postsynaptic responses were monitored by whole-cell recordings.
These recordings confirmed that electrically evoked inhibitory postsynaptic
currents (eIPSCs) are mediated solely by a9a10
nicotinic acetylcholine receptors (nAChRs) functionally coupled to
calcium-activated SK2 channels. Synaptic release occurred with low probability
when MOC-OHC synapses were stimulated at 1Hz. However, as the stimulation
frequency was raised, the reliability of release increased due to presynaptic
facilitation. In addition, the relatively slow decay of eIPSCs gave rise to
temporal summation at stimulation frequencies above 10 Hz. The combined effect
of facilitation and summation resulted in a frequency-dependent increase in the
average amplitude of inhibitory currents in OHCs. Thus, we have demonstrated
that short-term plasticity is responsible for shaping MOC inhibition and,
therefore, encodes the transfer function from efferent firing frequency to the
gain of the cochlear amplifier.