Chunk #26 — 2. Neural substrates for the negative emotional state associated with addiction — 2.1. Within-system neuroadaptations that contribute to the negative emotional state component of compulsivity
et al., 1992, 1996). Imaging studies in drug-addicted humans have consistently shown long-lasting decreases in the numbers of dopamine D2 receptors in drug abusers compared with controls (Volkow et al., 2002). In addition, cocaine abusers have reduced dopamine release in response to a pharmacological challenge with a stimulant drug (Volkow et al., 1997; Martinez et al., 2007). Decreases in the number of dopamine D2 receptors, coupled with the decrease in dopaminergic activity, in cocaine, nicotine, and alcohol abusers results in decreased sensitivity of reward circuits to stimulation by natural reinforcers (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.
