Brain-mediated protective interactions of histaminergic H2 and dopaminergic systems in rats.

Pretreatment with dopamine agonists (bromocriptine 2.5, L-dopa 2.5, apomorphine 0.05 mg/kg i.p.) and a histamine H2 receptor antagonist (cimetidine 50.0 mg/kg i.p.) was found to greatly reduce the haemorrhagic gastric lesions induced by 15-min pylorus ligation in rats. On the other hand, pretreatment with dopamine antagonists (haloperidol 5.0, sulpiride 1.0, domperidone 5.0 mg/kg i.p.) significantly aggravated these lesions. Cimetidine markedly diminished the ulcerogenic effect of haloperidol but not that of domperidone, suggesting a brain-mediated site for the protective interaction of cimetidine and dopamine systems.