Effects of Caffeine and Theophylline on Activity of Rats in Relation to Brain Xanthine Concentrations

Caffeine and theophylline were equally effective in increasing confinement motor activity when administered ip in doses up to 0.10–0.12 mmole/kg. Higher doses of caffeine produced some toxicity as evident from less stimulation of motor activity. Theophylline produced its peak effect at a dose of 0.17 mmole/kg (30 mg/kg). Doses of either xanthine as great as 0.25 mmole/kg produced much less activity than the optimum doses. Equimolecular doses of caffeine and theophylline produced approximately equal brain xanthine levels.