Effect of stimulation of cholinergic muscarinic receptors on norepinephrine accumulation in esophageal and gastric mucosa in rats

Abstract

An hour and half after injection of norepinephrine its concentration in the mucosa of the lesser curvature of the stomach increases and in the greater curvature decreases. Stimulation of muscarinic receptors with pilocarpine leads to a marked rise of norepinephrine concentration in the esophageal mucosa and in the mucosa of the lesser curvature. It is supposed that stimulation of muscarinic receptors of the gastrointestinal tract after injection of exogenous norepinephrine induces accumulation of this transmitter in structures with abundant cholinergie innervation. Selective norepinephrine accumulation in the mucosa of the esophagus and lesser gastric curvature is apparently due to its high permeability for norepinephrine contained in saliva.Key Words: catecholamines; esophageal mucosa; stomach Stimulation of exocrine gastrointestinal glands is accompanied by enhanced release of various growth factors (epithelial, nerve, etc.) [3,4,6,7]. This process depends on activity of sympathetic nervous system [7,8,10]. However, the possibility of accumulation of norepinephrine (NE) in esophageal and gastric mucosa induced by high plasma concentration of this transmitter against the background or without pilocarpineinduced stimulation of muscarinie receptors remains unclear. MATERIALS AND METHODSExperiments were carried out on 58 random-bred male rats weighing 250+50 g divided into 3 groups: intact rats, rats injected with 40 lxg/kg NE followed by stimulation of gastrointestinal muscarinie receptors with pilocarpine (1 mg/kg), and rats injected with NE (40-100 p.g/kg). Department of Pathological Physiology, Therapeutic Faculty, Moscow Medical Stornatological InstituteThe animals were deprived of food 24 h before the experiment to synchronize the function of exotrine gastrointestinal glands and had free access to water. The rats were narcotized with Nembutal (40 mg/kg) 20 min after NE injection. Forty-five minutes later the animals received pilocarpine (1 mg/kg), and secretory cycle was stimulated for 40 min. The contents of NE and epinephrine (E) in blood (0.5 ml) and mucosa specimens (10 nag) from the esophagus and the lesser and greater curvatures of the stomach were measured by high-performance liquid chromatography with electrochemical detection [1]. The data were processed statistically using the Student's t test. RESULTSIn control animals the concentration of NE in mucosa specimens far surpassed its plasma content. Plasma and tissue concentrations of E were much lower than those of NE (Table 1). Intraperitoneal injection of NE changed NE and E concentrations in the mucosa but not in the plasma: the content of NE increased

What’s new in the pathology, pathophysiology and management of benign esophageal disorders?

“…James et al 33 have looked at glutamine metabolism in the GI tract of the rat, while Sheving and Gardner 34 have investigated the circadian regulation of the cell cycle in the mouse esophagus. The remaining papers examine neuromuscular function of the esophagus 35 –56 …”