Neurophysiological findings and drinking levels in high-alcohol-drinking (HAD) and low-alcohol-drinking (LAD) rats

Background: Specific neurophysiological profiles, such as reduced P300 ampl itude or altered spectral power in the EEG, have been associated with a ris k for alcoholism in several clinical populations. In certain rodent models, high versus low alcohol consumption is associated with similar neurophysio logical differences. For example, alcohol-preferring (P) rats have increase d spectral power and decreased P300 amplitudes compared with alcohol-nonpre ferring (NP) rats. In the present study, the neurophysiological profiles of high-alcohol-drinking (HAD) and low-alcohol-drinking (LAD) rats were asses sed (1) to determine if their electrophysiological profiles are similar to P and NP rats and (2) to examine the relationship of these neurophysiologic al indices to ethanol drinking. Methods: Ethanol-naive HAD and LAD rats were implanted with cortical and am ygdalar recording electrodes. Baseline EEG and event-related potentials (ER Ps) then were assessed. Subsequently, all rats were trained to self-adminis ter ethanol by using a sucrose-substitution procedure. Results: Baseline EEG and ERP (i.e., pre-ethanol exposure) were assessed ba sed on line (HAD versus LAD) and actual ethanol consumption (high drinkers versus low drinkers). At baseline, ethanol-naive HAD rats displayed signifi cantly greater power in the cortical EEG and decreased amygdala N1 ERP ampl itude compared with ethanol-naive LAD rats. Similar EEG and ERP profiles ha ve been observed when P and NP rats are compared. No differences in P300 be tween lines were observed, but high-drinking rats, independent of line, had significantly decreased P300 amplitude in the amygdala compared with low-d rinking rats. Conclusions: These data suggest there are some similarities in EEG and ERP profiles of P and HAD rats compared with NP and LAD rats. Furthermore, the data suggest that decreased P300 amplitude in the amygdala is associated wi th increased limited access ethanol drinking.