(2S,3R)TMT-L-Tic-OH is a potent inverse agonist at the human delta-opioid receptor

We examined the pharmacologic effect of beta-methyl-2',6'-dimethyltyrosine-L-tetrahydroisoquine-3-carboxylic acid ((2 S,3 R)TMT-L-Tic-OH) on G protein activation in membranes prepared from Chinese Hamster Ovary cells transfected with cDNA of the human delta-opioid receptor. (2S,3R)TMT-L-Tic-OH inhibited G protein activation to 58% of basal with an EC50 of 0.72 nM as determined by [S-35]GTP gamma S binding. These findings suggest that (2S,3R)TMT-L-Tic-OH is a highly potent inverse agonist at the human delta-opioid receptor. (C) 1999 Elsevier Science B.V. All rights reserved.