GABA and glutamate/aspartate amino acids are important neurotransmitters in the neuronal circuits involved in the vestibulo-ocular reflex. Vestibular nuclei are controled by Purkinje cells and opposite vestibular nuclei and affect oculomotor nuclei through GABAergic neurons. There are three types of GABA receptors that are targets of GABAergic nerves: GABA
A, GABA
B and GABA
C receptors. GABA
A and GABA
B receptors are densely distributed in the cerebellum: GABA
A receptor is distributed in cerebellar Purkinje cells, deep cerebellar nucleui and vestibular nucleui, and GABA
B receptor is distributed in cerebellar Purkinje cells. GABA
C receptor is specifically distributed in the retina. GABA
A and GABA
C receptors are members of the transmittergate channel superfamily and their compositions are determined by the formation of pentameric structures. GABA
A receptor is composed of five kinds of subunit, α(α1-α6), β(β1-β4), γ(γ1-γ3), δand ρ, and possesses binding sites for benzodiazepines, barbiturates and neurosteroids. GABA
B receptor is a G-protein coupled receptor, although the receptor is the first discovered receptor forming heterodimers in the Gprotein coupled receptors. The functions of GABA
A and GABA
B receptors in the neuronal circuits that are involved in the vestiburo-ocular reflex have been investigated by histological and electrophysiological studies, but the role of the receptors in the vestibular functions have not been studied.
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