Differential increases of neurokinin B- and enkephalin-like immunoreactivities and their mRNAs after chronic haloperidol treatment in the rat.

Changes in neurokinin B-like immunoreactivity (NKB-IR) and neurokinin B mRNA were investigated after daily injection of haloperidol for 10 days on adjacent sections by means of immunocytochemistry and in situ hybridization in the caudate putamen of the rat. In the dorsal striatum the number of NKB immunoreactive perikarya and the staining intensity of striatal efferents increased. The number of NKB mRNA-expressing cells (45%) and the grain density over single positive cells (37%) were significantly higher after the neuroleptic treatment. The levels for enkephalin mRNA were uniformly increased throughout the rostrocaudal extent of the caudate putamen (85%). A main difference to the enkephalin system was that the dorsal pallidum was nearly devoid of NKB-IR in untreated as well as in haloperidol-treated animals. The present data for the first time provide evidence for the regulation of the biosynthesis of NKB after pharmacological intervention.