Functional correlates of heroin sensitization in the rat brain

The aim of the study was to measure the changes in cerebral energy metabolism and c-fos mRNA expression following challenge with heroin in drug-naive rats and in animals previously sensitized to the drug. Acute heroin administration to drug naive-rats produced a generalized metabolic depression. In contrast, challenge with heroin in drug-sensitized rats produced selective metabolic increases in structures belonging to the basal ganglia. These changes were accompanied by increased c-fos mRNA expression in the caudate-putamen nucleus. These results demonstrate that the process of sensitization to heroin is coupled to functional changes that are confined to the subcortical motor circuits of the basal ganglia.