1. Reserpine (5 mg/kg intraperitoneally) produced gastric mucosal vasoconstriction and injury in all rats within 6 h (injury score 38.8 ± 2.1 mm2, mean ± SEM). Coeliac ganglionectomy or the β-adrenoceptor-blocking drug propranolol (5–15 mg/kg) did not influence these effects of reserpine, but vagotomy protected the rats against them. The α-adrenoceptor-blocking drugs phenoxybenzamine and phentolamine at 5 mg/kg were protective against injury. However, a 10 mg/kg dose of either blocker was more effective (2.2 ± 0.5 mm2 and 3 ± 0.8 mm2, respectively, versus 38.8 ± 2.1 mm2, mean ± SEM, P <0.01) and a dose of 15 mg/kg afforded complete protection.

2. Methysergide, a 5-hydroxytryptamine receptor antagonist, produced a dose-dependent increase in the reserpine-induced injury; a significant (P <0.05) increase was noted with 15 and 20 mg/kg (47.5 ± 2.9 mm2 and 49.4 ± 2.2 mm2, respectively, versus 38.8 ± 2.1 mm2, mean ± SEM).

3. The results suggest that, in the rat, reserpine causes vagal α-adrenoceptor stimulation producing gastric mucosal vasoconstriction and injury. 5-Hydroxytryptamine is not implicated in the mechanism of this injury and affords protection against it.

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