ABSTRACT
Lines of rats were selectively bred to diverge bidirectionally from a randomly bred control line in the propensity to self-administer an opioid orally. These lines seek or avoid the high-potency opioid etonitazene in a situation in which it is presented continuously as a choice with water. Over seven generations, preferences were measured and selection pressure imposed to develop the accepting and rejecting lines. These animals represent the only contemporary selective breeding program for opioid preference or self-administration, and hold the promise of being a useful resource in the drug-abuse field.
Subject(s)
Benzimidazoles/pharmacology , Narcotics/pharmacology , Opioid-Related Disorders/genetics , Self Administration , Administration, Oral , Animals , Benzimidazoles/administration & dosage , Female , Male , Narcotics/administration & dosage , Opioid-Related Disorders/psychology , Rats , Rats, Inbred Strains , Sex CharacteristicsABSTRACT
Specific radioligand binding protocols were utilized to compare the affinity of morphine and the high-potency opioid etonitazene at mu 1, mu 2, delta, kappa 1 and sigma receptors. Both etonitazene and morphine displayed a mu 1-selective binding profile; however, etonitazene had a 2500-fold higher affinity at this receptor type. The latter result is consistent with the relative potencies or morphine and etonitazene in various behavioral tests.
