Neuromediators in aging and gastric mucosal injury.

The hypothesis that the improvement of neurochemical changes involving the brain dopaminergic and cholinergic systems in aged rats may be related to the their capacity of coping with stress has been investigated by testing the effect of various dopaminergic and cholinergic drugs on stress-induced gastric ulcer development. The model of cold-plus-restraint stress induced gastric lesions has been used in Sprague-Dawley rats aged 24 months, compared to young animals aged 2 months. An increased incidence of gastric ulcers was found in old animals. When these animals were treated with cholinergic or dopaminergic drugs, they showed a higher resistance to stress-induced biological modifications. The most potent drugs were found to be the cholinergic drug, physostigmine and the dopaminergic drug, deprenyl. Furthermore, the induction of hyperprolactinemia by pituitary homografts under the kidney capsule was also accompanied by a reduced incidence of cold-plus-restraint stress induced gastric lesions in aged rats. These results may suggest that the influence of neurotransmitter or hormonal factors on the brain may affect the response of aged rats to the application of physical stress.