Effects of autonomic nervous system on gastric damage by ethanol in the rat.

To study whether or not the autonomic nervous system influences the defense mechanisms of the gastric mucosa, groups of Sprague-Dawley rats were given stimulants and inhibitors of the different components of the vagus and celiac nerves before administration of absolute or 70% w/v ethanol. The effects of vagotomy and sympathectomy on "adaptive cytoprotection" were studied, as were the effects of blocking the muscarinic receptors and stimulation of beta-adrenergic receptors. We found that: (1) cholinomimetic agents and norepinephrine make the damage caused by 70% ethanol worse; (2) atropine is the only agent that fully protects against absolute ethanol; (3) vagotomy and sympathectomy abolish the effects of atropine and adaptive cytoprotection; and (4) beta-adrenergic stimulation replaces conditions that allow adaptive cytoprotection and the protection by anticholinergics. These results suggest that two different reflexes are triggered by ethanol: when low concentrations are given, the beta-adrenergic-mediated effect is prevalent, with protection of the mucosa; when high concentrations are given, the cholinergic-mediated effect is prevalent with damage of the mucosa.