A pentapeptide, methionine-enkephalin, which interacts with opiate receptors in the brain, was found to markedly potentiate the behavioral effects of DOPA when administered intraperitoneally into mice. These effects, which were even more striking with D-alanine-2-methionine-5-enkephalin but less with morphine, persisted at least two hours after systemic injection of the peptide. Only a weak effect of enkephalin was seen in a serotonin potentiation test. Systemic injections of enkephalin resulted in a significant reduction of footshock-induced fighting and slight reduction in audiogenic seizures in mice. The results suggest that the CNS effects observed after systemic administration of enkephalin may involve the dopaminergic receptor mechanism.
ASJC Scopus subject areas
- Biochemistry, Genetics and Molecular Biology(all)
- Pharmacology, Toxicology and Pharmaceutics(all)