DISTRIBUTION OF METABOTROPIC GLUTAMATE-RECEPTOR-7 MESSENGER-RNA IN THE DEVELOPING AND ADULT-RAT BRAIN

The large number of metabotropic glutamate receptor subtypes suggests diverse roles in brain function, although specific distribution patter ns can give clues to subtype-specific functions [Hayashi Y. el al. (19 93) Nature 366, 687-690; Nakajima Y. et al. (1993) J. biol. Chem. 268, 11868-11873; Nomura A. et al. (1994) Cell 77, 361-369; Ohishi H, et a l. (1993) Neuroscience 53, 1009-1018]. The metabotropic glutamate rece ptor mGluR7 is sensitive to the agonist L-2 amino-4-phosphonobutyric a cid, a presynaptic inhibitor of neurotransmitter release. We examined the anatomic distribution of mGluR7 messenger RNA expression by in sit u hybridization in the developing and adult rat central nervous system s. Our results demonstrate that mGluR7 messenger RNA is among the most widely distributed of metabotropic glutamate receptors in both the de veloping and adult rat nervous system and that mGluR7 messenger RNA is expressed in most neuronal groups known to respond to L-2-amino-4-pho sphonobutyric acid, including mitral cells of the olfactory bulb, gran ule cells of the dentate gyrus and neurons of the entorhinal cortex an d dorsal root ganglion. mGluR7 exhibits preferential expression in sen sory afferent pathways and is highly represented in the periventricula r zone of the hypothalamus, the latter implying a modulatory role for mGluR7 in neuroendocrine pathways. Most strikingly, the majority of ne urons at all levels of olfactory circuitry are among the areas of high est mGluR7 messenger RNA content. The anatomic distribution of mGluR7 messenger RNA suggests that mGluR7 activation may participate in the p rocessing of hippocampal, sensory and olfactory information.