Striatal neuropeptide Y neurones are under the influence of the nigrostriatal dopaminergic pathway: immunohistochemical evidence.

Selective unilateral 6-hydroxydopamine lesion of the nigrostriatal dopaminergic neurones in rats resulted, 12 to 90 days later, in a marked increase in the number of neuropeptide Y (NPY)-immunoreactive perikarya in the ipsilateral deafferented striatum compared to the contralateral intact side in the same animal and to both sides in control animals. The staining intensity of most positive cells also appeared to be enhanced in the deafferented striatum. These effects which can be interpreted as resulting from an increase in the intraneuronal levels of NPY may be accounted for by an increased production or a decreased metabolization of the peptide in the striatum deafferented from its dopaminergic input. The results therefore provide morphological evidence that the NPY-containing neuronal system of the striatum may undergo tonic influence from nigrostriatal dopaminergic afferents.