Anatomically distinct opiate receptor fields mediate reward and physical dependence

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Science  04 May 1984:
Vol. 224, Issue 4648, pp. 516-517
DOI: 10.1126/science.6324347


Rats never before exposed to opioids rapidly learned to press a lever for microinjections of morphine into the ventral tegmental area. Challenge by a narcotic antagonist produced no signs of physical dependence. Dependence was not seen after long-term morphine infusions into the ventral tegmentum but was seen after similar infusions into the periventricular gray region. Thus a major rewarding property of morphine is independent of the drug's ability to produce physical dependence. These data challenge models of drug addiction that propose physical dependence as necessary for the rewarding effects of opioids.