Experiments were performed to establish the development of cross tolerance between morphine and the C-terminal fragment of porcine β-lipotropin /LPH61-91, β-endorphin/ in rats. Repeated intracerebroventricular /ICV/ or peripheral administration of morphine induced tolerance both to morphine and β-endorphin. The tolerance induced by ICV administration of morphine was more pronounced than in the case of peripheral application. The results give support to the theory that at least in part similar sites and mechanisms are involved in the analgesic activity of morphine and the endorphins.
ASJC Scopus subject areas
- Biochemistry, Genetics and Molecular Biology(all)
- Pharmacology, Toxicology and Pharmaceutics(all)