Use of In Situ Hybridization and Immunohistochemistry to Study the Effects of Intranigral Injections of Colchicine on Enkephalin- and Substance P-Containing Neurons of the Limbic Forebrain

Abstract

The fact that the expression of genes encoding neuropeptides precursors and/or the levels of peptides in neurons may be regulated by nerve afferents has been well demonstrated in the neostriatum. In this material, it was shown that a chronic treatment with a dopaminergic antagonist resulted in a strong increase in the levels of enkephalins (ENK), correlated with an enhancement of preproenkephalin A (PPA) mRNAs (Chou et al. 1984; Tang et al. 1983; Normand et al. 1987; Romano et al. 1987; Le Moine et al. 1990). Likewise, similar changes in the levels of ENK and PPA mRNAs have been observed after unilateral dopaminergic denervation of the striatum by means of 6-hydroxydopamine (Thai et al. 1983; Young et al. 1986). In this last experimental model, by contrast, the levels of substance P (SP) and the mRNAs encoding this peptide were decreased (Voorn et al. 1987; Young et al. 1986). Furthermore, these data are substantiated by the fact that both ENK and SP containing neurons of the striatum receive direct inputs from dopaminergic nerve fibers (Kubota et al. 1986a,b).