Impaired outcome−specific devaluation of instrumental responding in mice with a targeted deletion of the AMPA receptor glutamate receptor 1 subunit

The present study evaluated the proposal that mice with a targeted deletion of the glutamate receptor 1 (GluR1) subunit of the AMPA receptor are impaired in using an instrumental or pavlovian signal to gain access to a representation of the sensory−specific motivational properties of a primary reward. In experiment 1, mice were trained to approach two goal boxes in a plus−maze; each goal box contained a different reward (sucrose solution vs food pellet). After acquisition, one of the rewards was devalued by an outcome−specific satiety procedure. Subsequent test trials performed in extinction showed an increase in the latency to enter the devalued goal arm, relative to the nondevalued goal arm in control but not GluR1−/− mice. In experiment 2, a similar outcome−specific satiety procedure was used to examine the effects of reward devaluation on an instrumental nose−poke response. During testing, control but not GluR1−/− mice decreased their rate of responding on a nose poke associated with a devalued reward. A subsequent choice test showed that GluR1−/− mice were able to discriminate between the devalued and nondevalued outcomes used in both experiments. These deficits mirror those seen after lesions of the basolateral amygdala and suggests that GluR1−mediated neurotransmission in this region contributes to encoding the relationship between sensory−specific aspects of reward and their incentive valu