The Location of Persistent Amphetamine-Induced Changes in the Density of Dendritic Spines on Medium Spiny Neurons in the Nucleus Accumbens and Caudate-Putamen

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Abstract
Repeated intermittent treatment with amphetamine increases the density of dendritic spines on medium spiny neurons (MSNs) in the nucleus accumbens (NAcc). The purpose of this study was two-fold: (1) to determine whether amphetamine has similar effects on MSNs in the caudate-putamen (CPu) and (2) to determine if this effect is localized to distal dendrites, the site of convergence of dopamine (DA) and glutamate synapses in the striatum. An amphetamine treatment regimen that produced behavioral sensitization increased the density of dendritic spines on MSNs in both the NAcc and dorsolateral CPu. This effect was long lasting, because it was evident 3.5 months after the discontinuation of drug treatment. The increase in spine density was confined to distal dendrites of MSNs, and was not apparent on dendrites close to the cell body. It is concluded that amphetamine may preferentially reorganize synapses at the site of DA–glutamate interaction in the striatum, which may alter DA–glutamate signaling and thereby contribute to some of the persistent behavioral and psychological consequences of repeated exposure to psychostimulant drugs.