Journal of Neuroscience, Vol 4, 1626-1638, Copyright © 1984 by Society for Neuroscience
The ventral pallidal projection to the mediodorsal thalamus: a study with fluorescent retrograde tracers and immunohistofluorescence
WS Young 3d, GF Alheid and L Heimer
We have examined rat basal forebrain projections to the mediodorsal
thalamic nucleus (MD) by making injections of retrogradely transported
fluorescent tracers into the MD. Additionally, in some animals, we also
stained sections for glutamate decarboxylase (GAD) by the indirect
fluorescent antibody technique. Our results demonstrate that the following
basal forebrain areas project to the MD: lateral orbital cortex, agranular
insular cortex superficial to claustrum, primary olfactory cortex, diagonal
band nuclei, ventral pallidum, and amygdala. A large number of labeled
cells are present in the olfactory tubercle, and these cells are almost
without exception located in dense GAD- positive ventral pallidal areas
rather than in striatal regions of the tubercle. This ventral pallidal
projection to the MD strengthens the concept of a ventral striatal-pallidal
system in parallel to the classic striatal-pallidal system which projects
to the ventral thalamus. These results are also discussed in relationship
to the olfactory system.