Requisite Role of Basolateral Amygdala Glucocorticoid Receptor Stimulation in Drug Context-Induced Cocaine-Seeking Behavior.

BACKGROUND: Exposure to cocaine-associated stimuli triggers a robust rise in circulating glucocorticoid levels. Glucocorticoid receptors are richly expressed in the basolateral amygdala, a brain region that controls the reinstatement of cocaine-seeking behavior upon exposure to a previously cocaine-paired environmental context. In the present study, we investigated whether glucocorticoid receptor stimulation in the basolateral amygdala is integral to drug context-induced motivation to seek cocaine in a rat model of drug relapse.

METHODS: Rats were trained to lever press for cocaine reinforcement in a distinct environmental context and were then given daily extinction training sessions in a different context. At test, the rats received bilateral glucocorticoid receptor antagonist (mifepristone; 3 or 10ng/hemisphere) or vehicle microinfusions into either the basolateral amygdala or the overlying posterior caudate-putamen (anatomical control region). Immediately thereafter, drug-seeking behavior (i.e., nonreinforced lever presses) was assessed in the previously cocaine-paired context and locomotor activity was assessed in a novel context.

RESULTS: Intra-basolateral amygdala, but not intra-posterior caudate-putamen, mifepristone dose-dependently attenuated drug context-induced cocaine-seeking behavior relative to vehicle, such that responding was similar to that observed in the extinction context. In contrast, mifepristone treatment did not alter locomotor activity.

CONCLUSIONS: These findings suggest that basolateral amygdala glucocorticoid receptor stimulation is necessary for drug context-induced motivation to seek cocaine.