NEUROKININ RECEPTOR MESSENGER-RNA LOCALIZATION IN HUMAN MIDBRAIN DOPAMINE NEURONS

The structurally related neurokinin peptides, substance P and neurokin in A, are found in abundance within the substantia nigra of a variety of mammalian species. Although it has been established recently that t he neurokinin-3 (NK3) receptor is the predominant neurokinin receptor found in rat substantia nigra and adjacent midbrain nuclei, the nature of the neurokinin receptor expressed in human midbrain has not been e lucidated. In the present study, neurokinin receptor messenger RNA(mRN A) content within rat and human midbrain were directly compared by usi ng quantitative in situ hybridization histochemistry. In contrast to t he high abundance of NK3 receptor mRNA within dopamine (DA) cells of t he rat midbrain, neurokinin-1 (NK1), but not NK3, receptor mRNA was lo calized to human midbrain DA cells. Within the human midbrain, the abu ndance of NK1 receptor mRNA differed significantly among the distinct DA cell-containing nuclei, with the highest level of expression seen i n several subdivisions of the substantia nigra. Thus different neuroki nin receptor subtypes apparently mediate the effects of substance P an d neurokinin A on human versus rat DA neurons. J. Comp. Neurol. 382:39 4-400, 1997. (C) 1997 Wiley-Liss, Inc.