The effects of administration of an inhibitory GABAergic or excitatory glutaminergic neurotransmitter into the lateral hypothalamic area (LHA) on gastric acids, an aggressive mechanism, and transepithelial potential difference (PD) and mucosal blood flow (MBF), defensive mechanisms, were examined in anesthetized rats, since lesions of LHA in these animals cause gastric mucosal damage and electrical stimulation stimulates gastric acids and antral contractions. Microinfusion of the inhibitory neurotransmitter, muscimol (GABA agonist) resulted in an increase in gastric acid secretion and in PD and MBF. The GABA antagonists picrotoxin and bicuculline methiodide, in contrast, decreased these three factors. The excitatory neurotransmitter L-glutamate induced only an increase of MBF. Thus, the GABAergic system in LHA stimulates the gastric functions, both defensive and aggressive mechanisms, while the glutaminergic system increases only a portion of the defensive system. The results suggest that there is a significant interaction between LHA and stomach functions.