Concentrations of ethanol in rebreathed air of rats: correlation with the discriminative stimulus effects of ethanol

We modified the method of Pohorecky and Brick (14) for determination of ethanol (ETOH) concentrations in rebreathed air of rats. Rats were injected with different doses (1-2 g/kg) of ETOH and both arterial blood and rebreathed air samples were collected at various time intervals (15-120 min) after administration. We found a very good correlation (r = .96) between ETOH concentrations in arterial blood and in rebreathed air; the blood/breath conversion factor (+/- SEM) was 3241 +/- 55. In the second part of the study, rats were trained to discriminate between IP administered ETOH (1.2 g/kg) and the saline vehicle (12 ml/kg). Training occurred 15 min after administrations. Once trained to reliably differentiate between ETOH/saline training sessions, different doses (0.6, 0.9 and 1.2 g/kg) of ETOH were examined at various time intervals (1, 7.5, 15, 30, 60, 120 and 240 min) after administrations on certain test days. The results indicated a good correlation (r = .65) between the discriminative stimulus effects of ETOH and the concentrations measured in rebreathed air. The behavioral effects as well as the concentrations of ETOH in rebreathed air have a fast onset. The peak occurred 7.5 min after injection, and both the stimulus effects and concentrations of ETOH were time- and dose-dependent.