Neurophysiological profiles of replicate line 2 high-alcohol-drinking (HAD-2) and low-alcohol-drinking (LAD-2) rats

A select number of electrophysiological findings have been demonstrated to differentiate rat lines selectively bred for high and low ethanol preference.

In the present study, EEGs and event-related potentials (ERPs) of high-alcohol-drinking (HAD) and low-alcohol-drinking (LAD) rats from replicate line 2 (HAD-2 and LAD-2) were assessed to determine if their neurophysiological profiles are similar to selected lines previously evaluated.

Rats obtained from Indiana University were implanted with cortical and amygdalar recording electrodes. Baseline EEG and ERPs were assessed in ethanol-naïve HAD-2 and LAD-2 rats. Animals subsequently were trained to self-administer ethanol by using a sucrose-substitution procedure.

Compared with LAD-2 rats, HAD-2 rats displayed greater parietal cortical power in the 6 to 32 Hz frequency range of the EEG. Greater parietal cortical peak frequency in the 2 to 4 Hz range and decreased frontal, parietal, and amygdalar peak frequencies in the 16 to 32 Hz frequency range were also seen. Compared with LAD-2 rats, HAD-2 rats had decreased P2 latency of ERPs recorded in the parietal cortex. HAD-2 rats also had greater frontal, parietal, and amygdalar P2 amplitudes, greater frontal and parietal cortical P1 amplitudes, and greater parietal cortical P3 amplitudes compared with LAD-2 rats. As anticipated, HAD-2 rats consumed significantly greater levels of sucrose, sucrose-ethanol, and ethanol over the course of the sucrose-substitution procedure compared with LAD-2 rats.

These data suggest that increased cortical power is associated with high ethanol preference in a number of selectively bred rat lines. However, unique electrophysiological characteristics may index alcohol preference in each line.