Enadoline (Free Base) is a kappa-opioid receptor agonist; PD 129290 (CAM 570; CI 977) is the S,S(-)-enantiomer; PD 129289 (CAM 569) is the corresponding R,R(+)-enantiomer. In human studies, it produced visual distortions and feelings of dissociation, reminiscent of the effects of salvinorin A. It was studied as a potential analgesic, but abandoned because of the dose-limiting effects of dysphoria, which could be expected from a κ-opioid agonist. There was mention of its potential in treating comatose head injury or stroke victims, where that type of side effect would be immaterial.
(Rac)-Enadoline ((Rac)-CI-977 free base) is a selective K-opioid receptor agonist that stereoselectively antagonizes clonic seizures induced by slow intravenous injection of N-methyl-DL-aspartate in mice[1].
[1] Singh L, et al. The anticonvulsant action of CI-977, a selective κ-opioid receptor agonist: a possible involvement of the glycine/NMDA receptor complex[J]. European journal of pharmacology, 1990, 191(3): 477-480.
