Discriminative stimulus effects of caffeine: tolerance and cross-tolerance with methylphenidate.
Twice daily injection of caffeine (30 mg/kg) for 3-1/2 days shifted the caffeine stimulus generalization curve to the right by 3-fold in rats trained to discriminate saline from 30 mg/kg of caffeine, and by 4-fold in rats trained to discriminate saline from 10 mg/kg of caffeine. The latter group was also tested for cross-tolerance with methylphenidate, a drug that generalizes completely with caffeine. Twice daily injection of caffeine (30 mg/kg) for 3-1/2 days increased the ED50 of methylphenidate for caffeine-appropriate responding from 1.5 to 5.5 mg/kg. Conversely, injections of methylphenidate (3.0 mg/kg) increased the ED50 of caffeine from 5.2 to 15 mg/kg. The development of symmetrical cross-tolerance to the discriminative effects of caffeine and to the caffeine-like discriminative effects of methylphenidate supports previous observations suggesting commonalities in the cellular bases of the stimulus properties of these drugs.
D000818:Animals; D002110:Caffeine / Q000494:pharmacology*; D004193:Discrimination Learning / Q000187:drug effects*; D004361:Drug Tolerance; D005795:Generalization, Stimulus / Q000187:drug effects; D008297:Male; D008774:Methylphenidate / Q000494:pharmacology*; D051381:Rats; D011919:Rats, Inbred Strains
D008774:Methylphenidate; D002110:Caffeine