PET Measures of Amphetamine-Induced Dopamine Release in Ventral versus Dorsal Striatum

Regional differences in dextroamphetamine (AMPH)-induced dopamine (DA) release in the baboon striatum were assessed using positron emission tomographic (PET) measures of [11C]raclopride specific binding to DA D2/D3 receptors acquired before and after AMPH administration. The magnitude of the reduction in [11C]raclopride binding, following AMPH administration, was two-fold greater in the anteroventral striatum (comprised of ventral caudate, anteroventral putamen, and nucleus accumbens) than the dorsal striatum (dorsal caudate). A simulation study demonstrated that any potential biases due to resolution (partial volume) and alignment effects were significantly smaller than the magnitude of the observed results. These regional differences in the sensitivity to AMPH are compatible with microdialysis evidence in rats indicating that the magnitude of DA release in response to AMPH concentrations in the range tested is greater in ventral than dorsal striatal regions. Post hoc tests involving measures in other striatal regions showed that the baseline DA D2/D3 binding was highest and the correlation between AMPH dose and change in [11C]raclopride binding most significant in the putamen.