Brain-stimulation reward, morphine-induced oral stereotypy, and sensitization: implications for abuse.

Early professionals believed that it was unlikely that anyone but the emotionally unstable received pleasure and became addicted to narcotic drugs. This position was well entrenched and influenced much of the thinking well into the latter half of the last century. Although the discovery of a brain reward system was made early in the 1950's it was not until 20 years later that this discovery was applied to the study of the mechanisms involved in the rewarding aspects of abused substances. Along this vein results will be shown in which opiate antagonist block the dopamine agonist activation of the brain reward system as well as the corollary. Sensitization of the reward system suggests that a driving force for drug use is 'liking' and not just 'wanting.' Basal changes in cerebral metabolic rates of glucose are seen in the presence of cues associated with morphine experience, giving evidence for the role of drug related cues in craving. Finally we asked the question 'Do old rats have as much fun as young rats?'