EFFECTS OF THE MUSCARINIC RECEPTOR AGONIST CARBACHOL AND OR ANTAGONIST PIRENZEPINE ON GASTRIC MUCUS SECRETION IN RATS

The effects of the muscarinic agonist carbachol on the secretion and a ccumulation of gastric mucus glycoprotein (mucin) were examined. Gastr ic mucin obtained from the soluble mucus, adherent mucus gel, and surf ace mucosal and deep mucosal layer was isolated and quantified. One ho ur after the subcutaneous administration of carbachol (0.08-80 mug/kg body weight) the deep corpus mucin content had decreased significantly (75% of control), corresponding to an increase (120% of control) in t he soluble mucin content with 0.8 mug/kg of carbachol treatment. These changes were counteracted by 10 mg/kg of pirenzepine (selective M1 an tagonist) pretreatment. On a single administration of 10 mg/kg of pire nzepine, deep corpus mucin tended to increase, and soluble mucin decre ased significantly (49% of the control). These two drugs failed to cau se any significant change in the mucin content of the surface and antr al deep mucosa or the adherent mucus gel. The muscarinic agonist and t he M1 antagonist are thus shown to accelerate the secretion and accumu lation, respectively, of mucin in the deep corpus mucosa. Thus intrins ic M1 receptor may possibly be involved in the secretion of mucin in t he gastric deep corpus mucosa.