DISTRIBUTION AND DEVELOPMENTAL REGULATION OF METABOTROPIC GLUTAMATE-RECEPTOR 7A IN RAT-BRAIN

To determine the regional and cellular distribution of the metabotropi c glutamate receptor mGluR7a, we used rabbit anti-peptide polyclonal-t argeted antibodies against the C-terminal domain of mGluR7a. Here we r eport that immunocytochemistry at the light-microscopic level revealed that mGluR7a is widely distributed throughout the adult rat brain, wi th a high level of expression in sensory areas, such as piriform corte x, superior colliculus, and dorsal cochlear nucleus. In most brain str uctures, mGluR7a immunoreactivity is characterized by staining of punc ta and fibers. However, in some regions, including the locus ceruleus, cerebellum, and thalamic nuclei, both cell bodies and fibers are immu nopositive. The changes in levels of mGluR7a during development were i nvestigated with immunoblotting and immunocytochemical analysis. Immun oblot analysis revealed that the levels of mGluR7a are differentially regulated across brain regions during postnatal development. In cortic al regions (hippocampus, neocortex, and olfactory cortex), mGluR7a lev els were highest at postnatal day 7 (P7) and P14, then declined in old er rats. In contrast, mGluR7a levels were highest at P7 in pons/medull a and cerebellum and decreased markedly between PT and P14. In these r egions, mGluR7a immunoreactivity was at similar low levels at P14 and P21 and in adults. Immunocytochemical analysis revealed that staining for mGluR7a was exceptionally high in fiber tracts in P7 animals relat ive to adults. Furthermore, the pattern of mGluR7a immunoreactivity in certain brain structures, including cerebellum, piriform cortex, and hippocampus, was significantly different in P7 and adult animals. In s ummary, these data suggest that mGluR7a is widely distributed througho ut the rat brain and that this receptor undergoes a dynamic, regionall y specific regulation during postnatal development.