DISTRIBUTIONS OF THE MESSENGER-RNAS FOR L-2-AMINO-4-PHOSPHONOBUTYRATE-SENSITIVE METABOTROPIC GLUTAMATE RECEPTORS, MGLUR4 AND MGLUR7, IN THERAT-BRAIN

The distribution of mRNAs for metabotropic glutamate receptors, mGluR4 and mGluR7, which are highly sensitive for L-2-amino-4-phosphonobutyr ate (L-AP4), was examined in the central nervous system of the rat by in situ hybridization. In general, the hybridization signals of mGluR7 mRNA were more widely distributed than those of mGluR4 mRNA, and diff erential expression of mGluR4 mRNA and mGluR7 mRNA was clearly indicat ed in some brain regions. Intense or moderate expression of mGluR4 mRN A was detected in the granule cells of the olfactory bulb and cerebell um, whereas no significant expression of mGluR7 mRNA was found in thes e cells. In other neurons or regions where mGluR7 mRNA was intensely o r moderately expressed, no significant expression of mGluR4 mRNA was o bserved. Such were the mitral and tufted cells of the olfactory bulb; anterior olfactory nucleus; neocortical regions; cingulate cortex; ret rosplenial cortex; piriform cortex; perirhinal cortex; CA1; CA3; granu le cells of the dentate gyrus; superficial layers of the subicular cor tex; deep layers of the entorhinal, parasubicular, and presubicular co rtices; ventral part of the lateral septal nucleus; septohippocampal n ucleus; triangular septal nucleus; nuclei of the diagonal band; bed nu cleus of the stria terminalis; ventral pallidum; claustrum; amygdaloid nuclei other than the intercalated nuclei; preoptic region; hypothala mic nuclei other than the medial mammillary nucleus; ventral lateral g eniculate nucleus; locus coeruleus; Purkinje cells; many nuclei of the lower brainstem other than the superior colliculus, periaqueductal gr ay, interpeduncular nucleus, pontine nuclei, and dorsal cochlear nucle us; and dorsal horn of the spinal cord. Both mGluR4 mRNA and mGluR7 mR NA were moderately or intensely expressed in the olfactory tubercle, s uperficial layers of the entorhinal cortex, CA4, septofimbrial nucleus , intercalated nuclei of the amygdala, medial mammillary nucleus, many thalamic nuclei, and pontine nuclei. Intense expression of both mGluR 4 mRNA and mGluR7 mRNA was further detected in the trigeminal ganglion and dorsal root ganglia, whereas no significant expression of them wa s found in the pterygopalatine ganglion and superior cervical ganglion . The results indicate differential roles of the L-AP4-sensitive metab otropic glutamate receptors in the glutamatergic nervous system. (C) 1 995 Wiley-Liss, Inc.