Suppression of sensory C fiber-mediated contractions by neuropeptide Y Y1 receptors in the guinea pig bronchi.

The aim of the study was to examine which neuropeptide Y (NPY) receptor types that are coupled to inhibition of sensory C fiber-mediated contractions of the guinea pig bronchi. NPY and PYY evoked a concentration-dependent inhibition of the electrically stimulated contractions. The Y1 receptor-selective antagonist BIBP3226 (1 microM) evoked a rightward shift of the NPY-induced response. Also the Y1 (and Y4-Y6) receptor agonist [Leu31,Pro34]NPY suppressed the stimulated contractions with a potency similar to the parent molecule. BIBP3226 (1 microM) also attenuated the response induced by [Leu31,Pro34]NPY. The Y2 receptor agonist [Cys2, Aoc524, D-Cys27]NPY suppressed the stimulated contractions at 1 microM only. NPY 2-36 was much less potent than NPY itself and pretreatment with BIBP3226 did not affect the inhibitory response. Human pancreatic polypeptide (Y4-Y6 receptor agonist) was inactive (< or = 1 microM). In conclusion, NPY is capable of suppressing sensory nerve-mediated contractions in the guinea pig bronchi mainly via Y1 receptors.