Clonidine administration increases neuropeptide Y immunoreactivity and neuropeptide Y mRNA in the rat cerebral cortex...

The effect of alpha 2 adrenoceptor stimulation on neuropeptide Y (NPY) and NPYmRNA expression was studied in the rat cerebral cortex. For receptor stimulation clonidine was used in a dose of 50 micrograms/kg s.c., 3 times at every 8 h; brains were studied 30-40 min after the last dose using radioimmunoassay (RIA), immunocytochemistry and in situ hybridization methods. The RIA of NPY did not show any significant changes in the NPY immunoreactivity (IR) level in the whole cortex, whereas the immunohistochemical analysis demonstrated an increase in the number of NPY-IR neurons in ventral cortical regions, especially in external cortical layers. In situ hybridization histochemistry of NPYmRNA also performed in ventral cortical sections showed that clonidine increased NPY synthesis in some cortical neurons. The obtained results indicate that the alpha 2 adrenoceptor stimulation by clonidine increases the NPY content and synthesis in rat cortical neurons.