Abstract
The present experiments examined the effects of muscarinic cholinergic receptor blockade in the nucleus accumbens (NAC) and medial prefrontal cortex (MPC) on intravenous cocaine self-administration. Adult male Sprague–Dawley rats were implanted with chronic indwelling jugular catheters and guide cannulae stereotaxically aimed at the NAC or MPC. The rats were then given the opportunity to intravenously self-administer cocaine (0.8 mg/kg/infusion) during daily 2-h sessions. Intra-NAC microinjections of methyl-scopolamine (2, 4, 8, 16, and 32 μg/side) or vehicle did not affect either the number of lever presses made or infusions delivered. On the other hand, intra-MPC injections of scopolamine significantly increased responding, although there was only a trend for an increase in the number of cocaine infusions. The effects of intra-MPC injections of scopolamine (8 and 16 μg/side) on locomotor activity were also evaluated. Intra-MPC injections of scopolamine (16 μg/side) produced significant increases in locomotor activity. However, these same microinjections decreased locomotor activity when the animals also received cocaine (15 mg/kg, i.p.). These results suggest that cholinergic neurotransmission at muscarinic receptors in the MPC is involved in regulating cocaine-maintained responding.
Published Version
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