A long ascending projection in the rat brain containing vasoactive intestinal polypeptide.

The effects of knife cut lesions of the medial forebrain bundle on the distribution of forebrain vasoactive intestinal polypeptide (VIP)-like immunoreactivity (VIP-LI) in the rat has been studied with radioimmunoassay and immunocytochemistry. The extent of depletion of tyrosine hydroxylase activity from corpus striatum was used to monitor lesion efficiency. Medial forebrain bundle lesions produced substantial depletions of VIP-LI from nucleus accumbens, hypothalamus, amygdala and bed nucleus of the stria terminalis ipsilateral to the lesion. No changes were seen in frontal cortex, olfactory tubercle, striatum and hippocampus. Possible origins of this long ascending projection, including an extensive group of cell bodies containing VIP-LI in the mesencephalic central grey matter, are discussed.