New glycosylpeptides with high antinociceptive activity.

The antinociceptive activity of two new synthetic glucoside and galactoside enkephalinamide analogues was studied. The effects produced by the new analogues were compared with those obtained with [D-Met2,Hyp5]enkephalinamide and with morphine. The analogues were injected into the fourth ventricle and intrathecally. Tail immersion and paw pressure behavioural tests were used to assess antinociception. One of the analogues studied, O1,5-[beta-D-galactopyranosyl] [D-Met2,Hyp5]enkephalinamide appears to be 57,000 times more potent than morphine.