Conditioned place preference produced by infusion of Met-enkephalin into the medial preoptic area

The conditioned place preference procedure was used to evaluate the rewarding properties of D-Ala2-Met5-enkephalinamide (DALA) after bilateral infusion into the medial preoptic area. Doses of 60, 250 and 100 ng/cannula were used. It was found that all doses of DALA produced place preference. This suggests that the medial preoptic area is a structure where opioid reward is produced in doses as low as those required in already established reward systems. The significance of this in relation to sexual reward is discussed.