DOSE-DEPENDENT SURMOUNTABILITY OF LOCOMOTOR-ACTIVITY IN CAFFEINE TOLERANCE

For two chronic intraperitoneal caffeine dose regimens (10 and 80 mg/k g per day), tolerance developed rapidly (2-3 days) to the stimulatory effects of caffeine on locomotor activity. However, surmountability of the tolerant activity rate levels by caffeine administration was dose dependent: Activity rate was restored fury by acute caffeine administ ration for the 10 mg/kg per day series, but not for the 80 mg/kg per d ay series. The extent of tolerance was also dose-dependent: Tolerance was incomplete for the low-dose daily caffeine series but complete for the high-dose series. Upon discontinuation of daily caffeine dosing, activity rate decreased to the original baseline levels for both chron ic series. Caffeine tolerance and the quantification of its surmountab ility may be explained by the pharmacokinetics of caffeine and the upr egulation of adenosine receptors.