Caffeine potentiation of apomorphine discrimination.
Rats were trained to discriminate between the stimulus properties of intraperitoneal 0.16 mg/kg apomorphine and saline in a two-lever, food-motivated operant task. Apomorphine, at doses different than the training dose, produced a dose-response relationship, whereas, caffeine (7.5-30 mg/kg) produced saline-like responding. However, co-administered of 15 mg/kg caffeine with 0.01, 0.02 or 0.04 mg/kg apomorphine potentiated the discriminative stimulus properties of these low apomorphine doses. This potentiation was antagonized by pretreatment with 0.25 mg/kg haloperidol. The results are consistent with the idea that caffeine, by virtue of being a phosphodiesterase inhibitor, may increase post-synaptic cyclic-AMP and this, in turn, may supersensitize the dopamine receptors and result in the potentiation of the apomorphine-induced dopaminergic responses.
D000818:Animals; D001058:Apomorphine / Q000494:pharmacology*; D002110:Caffeine / Q000494:pharmacology*; D000242:Cyclic AMP / Q000378:metabolism; D004298:Dopamine / Q000502:physiology; D004305:Dose-Response Relationship, Drug; D004357:Drug Synergism; D006220:Haloperidol / Q000494:pharmacology; D011287:Prejudice / Q000187:drug effects*; D051381:Rats
D002110:Caffeine; D000242:Cyclic AMP; D006220:Haloperidol; D001058:Apomorphine; D004298:Dopamine