Coexpression of GABA_BR1 and GABA_BR2 receptor subunits in the rat vestibular nucleus

The expression patterns of the two subunits of the metabotropic GABA_B receptor, GABA_BR1 and GABA_BR2, vary among various neural regions and their relative expression in the rat central vestibular system remains unknown. To identify the expression patterns of these two subunits of the metabotropic GABA_B receptor in the vestibular nucleus of adult rats, double immunofluorescence experiments were performed. GABA_BR1 or GABA_BR2 immunoreactivity was observed in neurons and neuropilar elements of the vestibular nuclear complex and its subgroups x and y. These neurons were oval, multipolar, fusiform or triangular in shape. In contrast to other brain regions, individual neurons or neuropil within the various vestibular subnuclei and subgroups displayed comparable levels of GABA_BR1 and GABA_BR2 immunoreactivity. Double immunofluorescence experiments further demonstrated the coexpression of GABA_BR1 and GABA_BR2 receptor subunits in individual central vestibular neurons. The present findings provide histological evidence of the heterodimeric nature of GABA_B receptors that mediate inhibitory neurotransmission in the rat vestibular nuclei. Copyright © 2009 S. Karger AG, Basel.