Expression of alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionate (AMPA) subunit mRNAs were assayed in the ventral mesencephalon of rats that received either a unilateral microinjection of the dopamine neurotoxin 6-hydroxydopamine (6-OHDA; Experiment 1) or repeated treatment with amphetamine (Experiment 2). GluR2 levels were decreased 1 and 3 days after the lesion, and GluR1 and GluR3 levels also showed a transient decrease at 1 day after the lesion. Repeated amphetamine treatment did not significantly alter GluR1-4 levels measured 30 min after the third or tenth amphetamine injection, even though locomotor sensitization was obtained. Thus, while the present results indicate that AMPA receptor subunits are associated with dopamine-containing cell bodies in the ventral mesencephalon, these transcripts may not be responsible for the development of amphetamine sensitization.