Effects of neuropeptide Y on alpha 1- and beta-adrenoceptor-stimulated second messenger systems in rat frontal cortex

Abstract

Neuropeptide Y (NPY) (1 μM) significantly reduced the basal cAMP concentration in slices of rat frontal cortex. However, NPY (10 −9–10 −6 M) did not alter the isoproterenol-stimulated (10 −9–10 −5 M) accumulation of cAMP in the frontal cortical slices, showing that Y 2 NPY receptors do not modulate the beta-adrenoceptor-stimulated adenylase cyclase activity. NPY (10 −8–2.5 × 10 −5 M) was also demonstrated to stimulate inositol phosphate accumulation in rat frontal cortex slices in a dose-dependent manner. However, NPY (1 μM) did not potentiate the ability of phenylephrine (5 × 10 −8–10 −4 M), an alpha 1-adrenoceptor agonist, to stimulate inositol phosphate hydrolysis. The combined effects of phenylephrine and NPY (1 μM) on inositol phosphate hydrolysis were additive, suggesting that the alpha 1-adrenoceptor and NPY Y 1 receptor sites are located on different postsynaptic sites in rat frontal cortex. This study demonstrates the existence of both Y 2 and Y 1 NPY receptors in the rat frontal cortex based on second messenger systems, but there does not appear to be an interaction of NPY with either alpha 1- or beta-adrenoceptors.