IMMUNOHISTOCHEMICAL STUDIES OF LOCALIZATION AND COLOCALIZATION OF GLUTAMATE, ASPARTATE AND GABA IN THE ANTERIOR THALAMIC NUCLEI, RETROSPLENIAL GRANULAR CORTEX, THALAMIC RETICULAR NUCLEUS AND MAMMILLARY NUCLEI OF THE RAT

Localization and possible co-localization of glutamate, aspartate and GABA immunoreactivities was examined in the anterior thalamic nuclei, retrosplenial granular cortex, thalamic reticular nucleus and mammilla ry nuclei of the rat by double antigen immunohistochemistry using diam inobenzidine and benzidine dihydrochloride in one series and double im munofluorescence labelling with rhodamine and fluorescein in a second series of animals. In three of these regions, retrosplenial granular c ortex, anterior thalamic nuclei, and mammillary nuclei, glutamate immu noreactivity was co-localized with aspartate immunoreactivity in a maj ority of the projection neurons (pyramidal neurons, predominantly in l ayers V and VI in retrosplenial granular cortex; rounded polygonal mul tipolar neurons throughout the rostrocaudal extent of the anterior tha lamic and mammillary nuclei). None of the cells showing glutamate and/ or aspartate immunoreactivity in these regions also displayed GABA imm unoreactivity, which was present in non-pyramidal-cells in the retrosp lenial granular cortex (chiefly in layers I-III) and in small numbers of cells within the anterior thalamic nuclei. In the thalamic reticula r nucleus, in contrast, most neurons were immunoreactive for GABA and in the majority of these neurons glutamate (and/or aspartate) immunore activity was co-localized with GABA. Copyright (C) 1996 Elsevier Scien ce B.V.