Chunk #34 — 3 Neural Substrates for the Negative Emotional State Associated with Alcoholism — 3.1 Within-System Neuroadaptations that Contribute to the Compulsivity Associated with the Dark Side of Alcoholism
Imaging studies in drug-addicted humans have consistently shown long-lasting decreases in the numbers of dopamine D2 receptors in alcoholics compared with controls (Volkow et al. 2002). Additionally, alcohol-dependent subjects had dramatically reduced dopamine release in the striatum response to a pharmacological challenge with the stimulant drug methylphenidate (Volkow et al. 2007). Decreases in the number of dopamine D2 receptors, coupled with the decrease in dopaminergic activity, in cocaine, nicotine, and alcohol abusers are hypothesized to produce a decreased sensitivity of reward circuits to stimulation by natural rein-forcers (Martin-Solch et al. 2001; Volkow and Fowler 2000). These findings suggest an overall reduction in the sensitivity of the dopamine component of reward circuitry to natural reinforcers and other drugs in drug-addicted individuals (Table 2).
