Role of dopamine D1 receptors in the prefrontal dorsal agranular insular cortex in mediating cocaine self-administration in rats.

RATIONALE: Orbital/insular areas of the prefrontal cortex (PFC) are implicated in cocaine addiction. However, the role of dopamine D1 receptors in mediating cocaine self-administration in these sub-regions remains unknown.
OBJECTIVES: To define the role of the dorsal agranular insular (AId) sub-region of the PFC, we investigated the effects of D1 receptor manipulation on self-administration behavior maintained by cocaine and cocaine-related stimuli.
MATERIALS AND METHODS: Rats were trained to lever press for cocaine (1 mg/kg) under a fixed-interval 5-min (fixed-ratio 5:S) second-order schedule of reinforcement in the presence of conditioned light cues and contextual sound cues. Intra-AId infusions of vehicle, the D1-like receptor agonist SKF 81297 (0.1, 0.2, 0.4 microg/side) or the D1-like receptor antagonist SCH 23390 (1.0, 2.0, 4.0 microg/side), were administered prior to 1-h self-administration test sessions. Food-maintained responding under a second-order schedule was examined in separate rats to determine if pretreatment with D1 ligands produced general impairments in responding.
RESULTS: Infusion of SKF 81297 (0.2 and 0.4 microg/side) reduced active lever responses during the first 30 min of 1-h test sessions, but did not influence cocaine intake. Infusion of 4.0 microg/side SCH 23390 reduced active lever responses and cocaine intake throughout the 1-h test sessions. Additionally, this dose of SCH 23390 disrupted food-maintained responding and intake.
CONCLUSIONS: D1 receptor agonists and antagonists in the AId have diverse consequences and time courses of action. D1 receptor stimulation in the AId may reduce the motivating influence of cocaine-related stimuli on responding whereas D1 receptor blockade in this PFC sub-region produces global disruptions in behavior.