Tyrosine hydroxylase-, neurotensin-, or cholecystokinin-containing neurons in the nucleus tractus solitarii send projection fibers to the nucleus accumbens in the rat.

A double-labeling method combining the retrograde tracing of horseradish peroxidase (HRP) with the immunocytochemical technique was used in the present study. The results suggest that the neurons containing tyrosine hydroxylase (TH), neurotensin (NT) or cholecystokinin (CCK) in the nucleus tractus solitarii (NTS) of the rat send their axons to the nucleus accumbens bilaterally with ipsilateral dominance. HRP-TH, HRP-NT or HRP-CCK double-labeled cell bodies were mainly located in the medial and the commissural subnucleus of the NTS. HRP-TH double-labeled cells were the largest in number, followed by HRP-NT cells, with HRP-CCK cells present in the lowest numbers.