A rapid and inexpensive technique for assessing the reinforcing effects of opiate drugs

KATZ, R. J. AND G. GORMEZANO. A rapid and inexpensive technique for assessing the reinforcing effects of opiate drugs. PHARMAC. BIOCHEM. BEHAV. 11(2) 231-233, 1979.--Adult male Sprague-Dawley rats were placed in an apparatus consisting of 2 distinctive interconnected chambers. Choice preferences developed and stabilized over three 30 min exposures. Central injection of morphine or an enkephalin analogue in conjunction with placement upon the non-preferred side caused apreference shift which was not evident in control subjects. Classical conditioning ofopiate ffects to distinctive nvironments may offer a novel means of assessing the hedonic effects of these compounds. Classical conditioning D-AIa ~ Leu-Enkephalinamide Morphine Opiate Reinforcement TRADITIONALLY, two methods have been available to pharmacologists wishing to investigate the reinforcing ef-fects of drugs. One method is self-administration [4, 10, 11], in which animals perform an operant ask to produce a con-tingent central or peripheral drug infusion. The second method involves altering ongoing patterns of intracranial self stimulation (e.g., rate or threshold) [1, 7, 10]. Other, al-though less commonly employed, techniques involve the es-tablishment of secondary (i.e., conditioned) reinforcement to stimuli paired with drugs and subsequent operant esting [4]. These procedures are highly effective but generally in-volve costly systems for programming contingencies and drug delivery. Moreover, often considerable xperimenter time is necessary for behavioral shaping. We have developed a simplified behavioral procedure for assessing the motivat-ing properties of drugs based upon classical conditioning. The present report demonstrates this technique using 2 opiate agonists, a long-lasting analogue of leu-enkephalin and morphine