The activity-regulated cytoskeletal-associated protein arc is expressed in different striosome-matrix patterns following exposure to amphetamine and cocaine.

The activity-regulated, cytoskeletal-associated gene, arc, is a brain-enriched immediate-early gene whose expression is rapidly induced in the striatum by dopamine receptor agonists. This rapid induction of arc in the striatum is similar to that of other early response genes such as c-fos, junB, deltafosB, fra, and NGFI-A, which code for transcription factors. Unlike these proteins, however, Arc is a cytoskeletal protein expressed not only in the nucleus of neurons but also in their dendrites. We investigated the patterns of Arc expression evoked in the rat striatum by acute exposures to two psychomotor stimulants, cocaine and amphetamine. Cocaine induced arc in striatal neurons that were broadly distributed within both striosome and matrix compartments of the caudoputamen. Amphetamine also evoked Arc expression in striatal projection neurons, but these were heavily concentrated in the striosomal compartment and only sparsely in the matrix compartment in the rostral striatum. The contrasting patterns of Arc expression evoked by cocaine and amphetamine parallel those of c-Fos, JunB, FRA, and NGFI-A expression induced by these two psychomotor stimulants. This difference in the action of cocaine and amphetamine at the level of protein expression may be linked to the different effects of these psychomotor stimulants on behavior.