Regional distribution of the cells expressing glycine receptor β subunit mRNA in the rat brain

The expression of mRNA of the β subunit of the glycine receptor was investigated in the rat by in situ hybridization histochemistry using an oligonucleotide probe specific to the sequence of the β subunit. Neurons expressing β subunit mRNA were widely and abundantly distributed in the rat brain from the olfactory bulb to the spinal cord. The pattern of distribution of cells containing β subunit mRNA in the lower brainstem was very similar to that of cells containing a₁ subunit mRNA. In addition, β subunit mRNA was strongly expressed by the neurons of the cerebral cortex, hippocampal formation and diencephalon as well as by the Purkinje cells where a₁ subunit mRNA expression is rare. These findings indicated that the glycine receptor is heterogeneous. The sites where strong labeling was noted were as follows. In the forebrain and diencephalon, strongly labeled neurons were abundant in the olfactory region, hippocampal formation, cerebral cortex, and thalamus. In the hippocampal formation, neurons in the subiculum, pyramidal cells in Ammon's horn, and neurons in the polymorphic layer of the dentate gyrus were strongly labeled. In the thalamus, the anterodorsal, reticular, parafascicular, and the subthalamic nuclei were strongly labeled. In the brainstem, the red nucleus, almost all of the motor neurons in the cranial motor nuclei innervating striated muscles, the trigeminal mesencephalic nucleus, the ventral tegmental nucleus of Gudden, and the pontine nucleus were strongly labeled. In the cerebellum, Purkinje cells in the Purkinje cell layer and all of the cerebellar nuclei were strongly labeled.