While the antagonist and full agonist produced similar effects on cocaine-seeking behavior, only the agonist increased response latency, suggesting that different processes mediate the effects of these drugs.

No abstract

Amygdala D1 receptors have been implicated in the motivating effects of cocaine-conditioned cues and cocaine itself, but the specific nucleus involved is unclear. Thus, we infused the D1 antagonist, SCH-23390, into the rostral basolateral amygdala (rBLA), caudal basolateral amygdala (cBLA), or central amygdala (CEA), and tested its effects on self-administration of cocaine, as well as reinstatement of extinguished cocaine-seeking behavior by cocaine-conditioned cues or cocaine itself. Two anatomical controls, the posterior regions of basal ganglia (BG) and somatosensory/insular cortices (CTX), were also examined. Cocaine self-administration was increased and cue and cocaine reinstatement were decreased by SCH-23390 infusion into every region when examined across the hour test session, with the exception that cBLA infusion did not alter cocaine reinstatement. In the first 20 min of the session, when SCH-23390 was more localized in the target sites, self-administration was increased by infusion into the CEA, cBLA, BG, and CTX, with lesser increases in the rBLA. Cocaine reinstatement was attenuated during the first 20 min only by infusion into the CEA, rBLA, and CTX. Cue reinstatement was not reliably observed in the first 20 min, but there was a trend for attenuation by infusion into the cBLA, and surprisingly, significant attenuations in the BG and CTX. The findings suggest that D1 receptors in subregions of the amygdala play differential roles in the reinforcing/motivational effects of cocaine, while the cue reinstatement effects are less clear. Further research is needed to examine the novel findings that neighboring regions of the BG and CTX may play a role in motivation for cocaine.

No abstract

The findings suggest that the attenuating effects of D1-receptor drugs on cocaine-seeking behavior during cocaine reinstatement are mediated by dopamine D1 receptors; however, it remains unclear whether the effects of these drugs on cocaine-seeking behavior during cue reinstatement are D1-receptor mediated. Nevertheless, it is evident that the attenuation of cocaine-seeking behavior by these drugs is not simply due to behavioral disruption.