Functional correlates of nicotine administration:: similarity with drugs of abuse

Changes in the local utilization of cerebral glucose resulting from administered drugs acting on the central nervous system can be evaluated quantitatively by the [C-14]2-deoxyglucose method. We report the findings obtained by the [C-14]2-deoxyglucose method that contribute to understanding the cerebral functional effects of drugs of abuse and discuss in particular the similarities between nicotine and other addictive drugs. A common consequence of the intravenous administration of psychomotor stimulants and opioids in the rat is the increase in glucose utilization in the shell of nucleus accumbens. This functional change is accompanied by increased local extracellular concentrations of dopamine. Altered functional activity and dopamine neurotransmission in the shell of the nucleus accumbens thus represent distinctive neurobiological markers of the addictive properties of several drugs, independently of the specific neurochemical mechanisms of action. It has recently been shown that the intravenous administration of a pulse of nicotine, at single-unit doses corresponding to those that maintain self-administration in the rat, produces neurochemical and metabolic changes in the shell of the nucleus accumbens that closely resemble those of psychomotor stimulants and opioids. The latter results demonstrate that nicotine shares with highly addictive drugs a distinct neurochemical and functional consequence. They therefore contribute to the neurochemical definition of the addictive nature of nicotine. These neurochemical and functional changes may contribute to the changes in expression of intracellular second messengers and neurotransmitter/receptor systems observed particularly in the shell following the administration of drugs of abuse.