Evaluation of the role of norepinephrine in the reinforcing effects of psychomotor stimulants in rhesus monkeys.

Rhesus monkeys were surgically prepared with intravenous catheters and allowed to self-administer cocaine (0.03-0.1 mg/kg/injection) under a fixed-ratio 10 schedule of drug delivery during daily 2-hour experimental sessions. When responding was stable for cocaine, saline or various doses of nisoxetine, a selective norepinephrine (NE) reuptake blocker, was substituted for cocaine for 5-7 consecutive sessions. Nisoxetine failed to maintain self-administration responding at any dose in 3 of 4 monkeys tested. Pre-session administration of the selective alpha 1 NE receptor blocker prazosin (0.2-1.6 mg/kg, IV, 15 minutes pre-session) did not systematically alter cocaine self-administration in any monkey. The results are in contrast to what has been found with DA agonists and antagonists and are consistent with the belief that NE does not play a primary role in the reinforcing properties of psychomotor stimulants.