GABA regulates the release of acetylcholine (ACh) at the medial olivocochlear (MOC) efferent-outer hair cell synapse through presynaptic GABAB receptors

WEDEMEYER , C; ZORRILLA DE SAN MARTÍN, J.; BALLESTERO, J.; TORBIDONI, AV; BETTLER; B; ELGOYHEN, A.B; KATZ, E.

Buenos Aires

Congreso; ISN Special Conference “Synapses and dendritic spines in health and disease”; 2012

Society for Neurochemistry

Outer hair cells (OHCs) of the mammalian cochlea are innervated by MOC efferent fibers. These OHC-MOC synapses are formed before the onset of hearing and maintained throughout the life of the animal. Although acetylcholine (ACh) is the main neurotransmitter, γ-aminobutiric acid (GABA) is also present at MOC synaptic terminals. We have previously shown that GABA modulates the cholinergic input at MOC-inner hair cell (IHCs) synapses by acting on presynaptic GABAB receptors. To further evaluate the role of the GABAB in the modulation of ACh release in MOC-OHC synapses, synaptic currents evoked by electrically stimulating the efferent fibers were recorded in voltage-clamped OHCs from isolated mouse organs of Corti at postnatal days 9-14. Preliminary results shows that the quantal content of evoked release was increased by the GABAB antagonist CGP35348. These results, suggest that GABA exerts a negative control on synaptic transmission through presynaptic GABAB receptors at MOC-OHC synapse, resembling MOC-IHC transient synapses.