Stimulation by enkephalins of D-glucose absorption in rabbit ileum

Abstract.

In intact tissue, DAGO ([D-Ala², MePhe⁴, Gly-ol⁵]enkephalin; 10⁻⁵ M; μ-ligand; addition on the serosal side) stimulated D-glucose absorption and D-glucose-dependent variations in short-circuit current (ΔI_sc,glu); naloxone (10⁻⁶ M) antagonized these effects. DADLE ([D-Ala², D-Leu⁵]enkephalin, mainly a δ-ligand; 10⁻⁵ M) and (pCl-Phe⁴)-DPDPE ([D-pen², p-chloro-Phe⁴, D-Pen⁵]enkephalin, a more selective δ-ligand; 10⁻⁵ M) did not significantly stimulate ΔI_sc,glu (addition on the serosal side). In the absence of the muscularis and myenteric plexus or using intact tissue treated with tetrodotoxin (TTX; 3×10⁻⁷ M), DAGO was unable to increase ΔI_sc,glu . Addition of DAGO to the mucosal side did not induce any variations in ΔI_sc,glu . In conclusion, DAGO is able to increase D-glucose absorption by interacting with μ-receptors located in the myenteric plexus.