Efferent projections from the anterior nucleus of the solitary tract of the hamster.

The efferent projections from the anterior nucleus of the solitary tract (NST) of the golden hamster (Mesocricetus auratus) were determined using both anterograde and retrograde techniques. Injections of [3H]leucine were made into the anterior NST in regions responsive to gustatory stimulation of the anterior tongue. Ascending projections to the parabrachial nuclei (PBN) were evident as were projections within the NST and subjacent reticular formation. The cells of origin for both ascending and descending pathways were characterized by deposits of HRP into the PBN and caudal medulla. Cells projecting to the PBN were located in the dorsal and dorsolateral anterior NST in contrast to cells from the ventral region of the anterior NST which project within the medulla. Neurons in the reticular formation ventral to the anterior NST project to both regions. These local projections adjacent to oral motor nuclei provide an anatomical basis for the anterior nucleus of the solitary tract to influence oro-motor responses.