Immunohistochemical localization of GABA_B receptor 1 subtype in the brainstem motor nuclei of the rat

The localization and distribution of γ-aminobutyric acid B receptor 1 subtype (GABA BR1) in the rat brainstem motor nuclei was investigated by immunocytochemical staining technique. Intensely and densely stained GABA BR1-like immunoreactivity (-LI) neuronal cell bodies, fibers and terminals were observed in the Edinger-Westphal nucleus, superior salivatory nucleus, ambiguus nucleus and dorsal motor nucleus of the vagus nerve. Medium density and densely stained GABA BR1-LI neuronal cell bodies, fibers and terminals were found in the trigeminal motor nucleus and facial nucleus. Medium density and lightly stained GABA BR1-LI neuronal cell bodies, fibers and terminals were observed in the oculomotor nucleus, trochlear nucleus and hypoglossal nucleus. Sparsely and lightly stained GABA BR1-LI neuronal cell bodies, fibers and terminals were observed in the abducens nucleus and inferior salivatory nucleus. The present results indicate that the distribution of GABA BR1-LI structures in the different brainstem motor nuclei is significantly different.