Individual differences in dopamine release but not rotational behavior correlate with extracellular amphetamine levels in caudate putamen in unlesioned rats

It has been postulated that differences in pharmacokinetics do not contribute to the well-known individual variability in response to amphetamine (AMPH), but this is yet to be investigated thoroughly. Therefore, rotational behavior of outbred rats (Sprague-Dawley, 4 months old) was recorded during microdialysis sessions and striatal microdialysate was analyzed concomitantly for AMPH and dopamine concentrations after a single injection of 2.5 mg/kg AMPH SC. Three hours later these rats received three doses of 5 mg/kg AMPH SC (spaced 2 h apart) and their brain temperature was recorded every 20 min. The most important findings were: 1) the increase in extracellular dopamine was highly correlated with the corresponding peak AMPH levels in the microdialysate; 2) the peak dopamine level in response to 2.5 mg/kg AMPH was predictive of the hyperthermic response observed during 3 x 5 mg/kg AMPH and 3) high versus low rotators differed neither in their AMPH nor in their dopamine extracellular striatal concentrations.