In summary, GluA1−/− animals were impaired in expressing conditioned place preference when tested in drugged state. Importance of state-dependency for neurobiology of addiction has previously been suggested [1], and the present data are important in suggesting a role for GluA1 subunit-containing AMPA receptors in morphine state-dependency. AMPA receptor-mediated plasticity in response to the drugs of abuse has previously been suggested to underlie at least the initial steps in the development of drug dependence and addiction [12], and our data further strengthen the significance of AMPA receptors in these processes.
