Effect of 6-hydroxydopamine on neuropeptide Y and corticotropin-releasing factor expression in rat amygdala

The influence of dopaminergic denervation on neuropeptide Y and corticotrop in-releasing factor-containing neurons in the amygdala was investigated in rats by examining the effects of a selective, unilateral 6-hydroxydopamine lesion of mesencephalic dopaminergic neurons in both the substantia nigra a nd the ventral tegmental area on these peptides and their messenger RNA exp ression, observed eight to 10 days after the lesion. The studies were condu cted by immunocytochemical and in situ hybridization methods. Neuropeptide Y or corticotropin-releasing factor-immunoreactive neurons were counted in sections of the amygdala under a microscope, and the messenger RNA expressi on was measured as optical density units in autoradiograms. A significant i ncrease in both neuropeptide Y and corticotropin-releasing factor messenger RNA expression was found in the amygdala on the lesioned side in compariso n with the contralateral one, as well as with the ipsilateral side of vehic le-injected controls. Immunohistochemical studies showed that the number of neuropeptide Y-immunoreactive neurons increased in the whole amygdala on t he lesioned side. At the same time, the number of corticotropin-releasing f actor-immunoreactive neurons grouped in the central amygdaloid nucleus decl ined, and so did the staining intensity. The obtained results indicate that dopaminergic denervation stimulates the synthesis of neuropeptide Y and corticotropin-releasing factor in rat amygd ala, but the peptide levels are differently regulated, which points to a di verse release of these peptides. (C) 1999 IBRO. Published by Elsevier Scien ce Ltd.