DISTRIBUTION OF GABA(A) RECEPTOR-ALPHA-1 SUBUNIT-LIKE IMMUNOREACTIVITY IN COMPARISON WITH THAT OF ENKEPHALIN AND SUBSTANCE-P IN THE RAT FOREBRAIN

The gamma-aminobutyric acid-A receptor consists of several subunits. I n this immunohistochemical study we investigated the regional distribu tion of the al subunit with an antibody directed against a specific am ino acid sequence (1-9) of the alpha 1 subunit. We compared the distri bution pattern of the alpha 1 subunit-like immunoreactivity with that of substance P- and enkephalin-like immunoreactivities in adjacent sec tions of the rat forebrain. alpha 1 subunit-like immunoreactivity appe ared in the form of varicosities and fibers. A band-like terminal stai ning pattern (woolly fibers) that has been shown by others for substan ce P- and enkephalin-like immunoreactivity is also observed for alpha 1 subunit-like immunoreactivity. In contrast to substance P and enkeph alin, numerous alpha 1 subunit-like immunoreactive perikarya were foun d. The highest density of al subunit-like immunoreactive fibers and pe rikarya was found in the pallidal areas and the substantia nigra pars reticulata whereas the nucleus accumbens and the caudate putamen displ ayed a low density. oil subunit-like immunoreactive neurons resembled typical pallidal neurons. Some of these neurons were pericellularly st ained with enkephalin-like immunoreactive varicosities in the dorsal p allidum. The distribution pattern of alpha 1 subunit-like immunoreacti vity reflects a partial overlap with the substance P and enkephalin sy stem although a differential distribution to each of these peptides wa s observed for cell bodies, fibers, and axon terminals. (C) 1995 Wiley -Liss, Inc.