The regional distribution of d-amphetamine and local glucose utilization in rat brain during continuous amphetamine administration

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Abstract
The distribution of radioactivity following administration of either [3H]d-amphetamine or [3H]2-deoxy-d-glucose was examined by scintillation counting of 22 microdissected brain regions from rats pretreated with either acute or continuous amphetamine, or continuously administered labeled d-amphetamine. Animals continuously administered drug were sacrificed in behaviorally distinct stages of the continuous amphetamine syndrome, a potential animal model of amphetamine psychosis. Both isotopes were heterogeneously distributed within brain, and their distributions were differentially affected by acute or continuous amphetamine regimens. While the distribution of either isotope in naive rats was characterized by greatest concentrations of counts in rostral rather than caudal regions, and grey-matter rather than white-matter structures, continuous amphetamine administration resulted in progressively increased retention of amphetamine by mesolimbic but not nigrostriatal brain regions; this was accompanied by locally enhanced levels of glucose utilization. This effect was predominantly localized in the nucleus accumbens, which exhibited the greatest retention of amphetamine and greatest relative increase in glucose utilization of any region studied during that stage of the continuous amphetamine syndrome thought to best model amphetamine psychosis. Alterations in amphetamine distribution and local levels of neural activity may reflect a change in the principal locus of control of amphetamine effects within brain as animals progress through the stages of the continuous amphetamine syndrome.