Selective opiate tolerance in the guinea-pig ileum is not associated with selective dependence

Opiate dependence attributable to specific types of opiate receptors was studied in the isolated guinea-pig ileum made tolerant/dependent in vivo to a specific narcotic agonist. Apparently, induction of dependence of mu-receptors was associated with dependence of kappa-receptors and vice versa. These investigations involved the use of the irreversible mu-receptor antagonist beta-funaltrexamine to provide preparations with functional kappa-receptors only. The documented cross-dependence between different opiate receptor types suggests a common system with which these opiate receptors interact.