10.前庭動眼反射弓におけるGABA受容体

抄録

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.