Neuroanatomical boundaries of the reward-relevant opiate-receptor field in the ventral tegmental area as mapped by the conditioned place preference method in rats

The conditioned place preference produced by morphine microinjected into the ventral tegmental area was studied in rats. Cannula placements were varied along the rostrocaudal plane to the determine the approximate anatomical focus of morphine's rewarding effect. Microinjections within a 1.4-mm range produced a significant change in place preference suggesting that morphine injected into this zone is rewarding. Injection sites rostral and caudal to this zone were ineffective as were injections ventral to this region. The approximate anatomical boundaries of the reward-relevant opiate-receptor field within the ventral tegmental area correspond well with the distribution of the A₁₀ dopamine-containing cell bodies.