Effects of d- and l-amphetamine on food intake: evidence for a dopaminergic substrate.

The present experiment examined the effects of d- and l-amphetamine on the intake of sugar, sweetened rat chow and unsweetened rat chow in free feeding rats. Rats were injected IP with 4 doses of d- or l-amphetamine (0.0, 0.125, 0.50 and 2.00 mg/kg). Regardless of drug condition, animals were found to prefer sugar over sweetened or unsweetened chow. d-Amphetamine significantly increased food intake at 0.125 and 0.50 mg/kg doses but not at 2.00 mg/kg. l-Amphetamine had no significant effects at any dose. Further, d-amphetamine significantly increased sugar intake but not sweetened or unsweetened chow. Since d- and l-amphetamine are equipotent at releasing noradrenaline, while d-amphetamine is 2 to 5 times more potent at releasing dopamine, the results suggest that d-amphetamine-induced feeding is associated with activation of a dopaminergic substrate.