Alcohol and the auditory brain-stem response, brain temperature, and blood alcohol curves: explanation of a paradox.

A previous study found temperature-independent effects of alcohol upon the auditory brain-stem response (ABR): another found only temperature-dependent effects. To understand these paradoxical results, we measured the ABR and brain temperature in unrestrained rats before and after 3 alcohol doses (0.5, 2.5 and 5.0 g/kg). In a separate experiment, blood ethanol concentration (BEC) curves were determined for the same 3 alcohol doses. Integration of dose- and time-related effects of alcohol upon the ABR, brain temperature, and BEC suggested that alcohol has both temperature-dependent and temperature-independent effects, which vary according to dose and BEC curve phase. Temperature-dependent effects are likely during a BEC curve falling phase with a steep slope, following a high alcohol dose. Temperature-independent effects are likely during a BEC curve falling phase with a flatter slope, when BEC is still high following a moderate alcohol dose, or during a BEC curve rising phase soon after alcohol administration. The two previous studies with contradictory results each used procedural combinations likely to produce their respective results. Although both research groups administered similar alcohol doses, their alcohol solutions, administration routes, and time of ABR recording differed; consequently, they probably recorded ABR during different portions of BEC curve falling phases, which differed in slope. In view of the complex interactions among alcohol effects, BEC curve phase, temperature, and the ABR, we recommend temperature measurement during alcohol-ABR studies.