The effects of mepyramine and cimetidine on the motor responses to histamine, cholecystokinin, and gastrin in the fundus and antrum of isolated guinea-pig stomachs.

Guinea-pig stomachs were isolated in organ baths, and recordings made of fundal and antral responses. Cholecystokinin (CCK-PZ), 0.38 U/ml, gastrin, 0.05 microgram/ml, and acetylcholine, 10(-4)M, produced typical responses: raised base line in the fundus and increased amplitudes of rhythmic contractions in the antrum. The antral responses to gastrin were too small to quantitate. Both fundal and antral responses to 5 x 10(-4)M histamine consisted of an increase in base line without an alteration in amplitudes. Mepyramine, 3.2 x 10(-5)M, reduced the spontaneous activity in the fundus. It also inhibited fundal responses to gastrin and responses to histamine and CCK-PZ in both pouches. The fundal response to acetylcholine was unaffected by mepyramine, but the antral response seemed to be partially reduced (p less than 0.06). Cimetidine affected neither spontaneous activity nor motor responses. The results indicate that the motor response to histamine is mediated via H1-receptors and that these receptors may also be involved in the fundal response to CCK-PZ and gastrin. The inhibition of the antral responses by mepyramine may be due to unspecific anticholinergic action.