E (2000) Evidence for Y1-receptor-mediated facilitatory, modulatory cotransmission by NPY in the rat anococcygeus muscle. J Pharmacol Exp Ther 294:38–44

The potential role of neuropeptide Y (NPY) as a neuromodula-tory cotransmitter was investigated in rat anococcygeus mus-cle. The effects of NPY on contraction to norepinephrine or adrenergic nerve stimulation and on relaxation to nonadrener-gic, noncholinergic nerve stimulation were analyzed. Norepi-nephrine-induced contraction was enhanced by NPY (0.1 mM). The Y1 receptor antagonist BIBP 3226 (1 mM) completely re-versed this effect. NPY (0.01 or 0.1 mM) increased contractions induced by electrical field stimulation of sympathetic nerves. This increase was reduced by BIBP 3226 (1 mM), indicating Y1 receptor involvement. NPY (13–36) a Y2 receptor agonist, at 0.1 mM but not 0.01 mM, caused an increase of the nerve-induced contraction, which was reversed by BIBP 3226 (1 mM), indicat-ing no Y2 receptor involvement. BIBP 3226 (1–1 mM) produce