CLONIDINE ADMINISTRATION INCREASES NEUROPEPTIDE-Y IMMUNOREACTIVITY AND NEUROPEPTIDE-Y MESSENGER-RNA IN THE RAT CEREBRAL-CORTEX NEURONS

The effect of alpha(2) adrenoceptor stimulation on neuropeptide Y (NPY ) and NPYmRNA expression was studied in the rat cerebral cortex. For r eceptor stimulation clonidine was used in a dose of 50 mu g/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 hybridi zation 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 co rtical layers. In situ hybridization histochemistry of NPYmRNA also pe rformed in ventral cortical sections showed that clonidine increased N PY synthesis in some cortical neurons. The obtained results indicate t hat the alpha(2) adrenoceptor stimulation by clonidine increases the N PY content and synthesis in rat cortical neurons.