Metabotropic glutamate receptors group I are involved in cochlear neurotransmission.

All three types of ionotropic glutamate receptors, AMPA, NMDA and kainate, contribute to the neurotransmission between inner hair cells (IHC) and afferent neurons in the mammalian cochlea. We used microiontophoretic techniques to investigate whether metabotropic glutamate receptors group I (mGluR I) are also involved in the transmission of IHC afferents of the guinea pig. The mGluR I agonist DHPG produced an increase in afferent firing, which lasted significantly longer than that of the ionotropic agonists AMPA and NMDA. The activation was reversibly blocked by the mGluR I antagonist AIDA in a dose-dependent manner. AIDA also diminished spontaneous activity, but only slightly affected the AMPA- or NMDA-induced firing rate. Our results suggest that mGluR I are involved in peripheral auditory processing.