AMPA-receptor involvement in c-fos expression in the medial prefrontal cortex and amygdala dissociates neural substrates of conditioned activity and conditioned reward

Exposure to an environment, previously conditioned to amphetamine (1 mg/kg, i.p.), induced locomotor activity and c-fos expression (a marker for neuronal activation) in the mouse medial prefrontal cortex (mPFC) and amygdala; acute or repeated amphetamine (1 mg/kg, i.p.) administration induced c-fos expression additionally in the nucleus accumbens. An alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionate (AMPA)-receptor antagonist, 2,3-dihydroxy-6-nitro-7-sulphamoyl-benzo(f)quinoxaline (NBQX), blocked expression of conditioned activity, and prevented the increase in c-fos expression in mPFC, implicating mPFC AMPAergic transmission in the conditioned component of behavioural sensitization to amphetamine. NBQX failed to block the expression of amphetamine-conditioned place preference, a measure of conditioned reward, or conditioned c-fos expression in the amygdala, an area implicated in the expression of conditioned place preference. These findings indicate that the conditioned components of behavioural sensitization depend on AM PA-receptor-mediated activation in mPFC, but that conditioned reward does not.