Sympatho-adrenal system involved in the inhibitory effects of nicotine on the vagally stimulated gastric acid output and mucosal blood flow in rats.

The peripheral effects of nicotine on gastric functions were examined in anesthetized rats. The intravenous infusion of nicotine inhibited the increase in vagally stimulated gastric acid output. This inhibitory effect was abolished by phentolamine or by a combined treatment with bilateral adrenalectomy and reserpine. Nicotine had a dual effect on the gastric mucosal blood flow (MBF): inhibition followed by an increase. The inhibitory effect was abolished by phentolamine or by the combination with reserpine and adrenalectomy. Propranolol or adrenalectomy abolished the increase. These various effects of nicotine on the gastric acid output and MBF were not attenuated by bilateral splanchnicectomy. These results suggest that nicotine acts directly on both the adrenal medulla and postganglionic sympathetic neurons in the gastric wall, namely by acting on alpha-adrenoceptors, thus decreasing acid output and MBF, and by activating beta-adrenoceptors thus slightly increasing MBF.