Involvement of the D-2 dopamine receptor in the neuroleptic-induced decrease in nigral substance P.

Repeated treatment with, but not single administration of drugs which impair dopaminergic transmission produced a consistent reduction in substance P immunoreactivity in the rat substantia nigra. This effect appears to be related to the D-2 dopamine receptor function as the blockade of this receptor subtype by selective antagonists produced effects qualitatively similar to those produced by drugs lacking selectivity for different subclasses of dopamine receptors.