Differences in gastroprotective processes in 6- to 8- and 14- to 16-week-old rats.

The gastroprotective effect of opioid peptides, prostaglandin E2 and capsaicin against acidified ethanol-induced gastric mucosal damage in young mature rats of different (6-8 and 14-16 weeks) ages has been investigated. It was found that gastric mucosal damage was more severe in 14-16 weeks old rats. The gastroprotective effect of opioid peptides--[D-Ala2, D-Leu5]-enkephalin (DADLE), deltorphin II, [D-Ala2, Phe4, Gly5 -ol]-enkephalin (DAGO) and beta-endorphin--given either intracerebroventricularly (0.6, 3.3, 0.2, and 0.01 nmol/rat, respectively) or subcutaneously (825 and 960 nmol/kg, respectively) was highly reduced in 14-16 weeks old rats. The mucosal protective action of orally administered capsaicin (1600-3200 nmol/kg) and PGE2 (280-560 nmol/kg) was also diminished in 14-16 weeks old animals. Both ACTH and corticosterone plasma levels were significantly higher in 14-16 weeks old rats. These results suggest that the gastric mucosal susceptibility to ethanol and the gastroprotective effect of opioid peptides, capsaicin and PGE2 are age-related.