Neuropeptide Y augments adrenergic contractions at feline lower esophageal sphincter

The purpose of this study was to determine the anatomic and physiological interactions between neuropeptide Y (NPY) and adrenergic transmitters at the feline lower esophageal sphincter (LES). Intraluminal pressures of the esophagus, LES, and gastric fundus were recorded in anesthetized cats. In a separate group of cats, gastroesophageal junctions were removed after locating the LES manometrically. Adjacent sections were stained with antibodies for NPY and tyrosine hydroxylase (TH). Indirect immunofluorescence revealed staining of TH- and NPY-like immunoreactive (LI) nerves in the circular muscle of the LES. Staining was also present for NPY-LI in longitudinal muscle, muscularis mucosa, periarterial nerves, and nerves and cell bodies of the myenteric plexus of the LES. In vivo, NPY produced a biphasic effect at the LES with an initial contraction (lasting approximately 30 s) followed by a relaxation (lasting approximately 3 min). NPY at the dose giving 50% of the maximum response (10(-6) g/kg) induced a contraction of 14.8 +/- 5.0 mmHg (P less than 0.05) followed by a decrease of basal LES pressure from 29.2 +/- 4.7 to 19.4 +/- 2.9 mmHg (P less than 0.01). Propranolol and phentolamine had no influence on either effect of NPY.(ABSTRACT TRUNCATED AT 250 WORDS)