al., 2006). For instance, early-onset of ethanol drinking in P rats has been associated with higher density of cortical and hippocampal seronin-1A (5-HT1A) receptors and lower density in the expression of dopamine (DA) D2 receptors in the ventral tegmental area (VTA) (for review, see McBride et al., 2005). Previous studies in our laboratory in P and NP rats have also shown that differences in glutamate and GABA function may play an important role in their ethanol preference. We found that the acute effects of MK-801, an NMDA receptor antagonist, and diazepam, a GABA/benzodiazepine receptor agonist, on cortical and hippocampal EEG are significantly attenuated in P rats, in comparison to NP rats (Robledo et al., 1994). Whether deficits in these neurotransmitter systems play a role in the attenuation in evoked delta and alpha/beta phase locking in P rats remains unclear. While findings from the present studies contribute to our understanding of the neurophysiological mechanisms regulating the reduction in P3 amplitudes in P rats, further studies are needed to determine the relationship between the expression of these neurophysiological endophenotypes and the genetic profile of the P and NP rats. Understanding the relationship between evoked oscillatory activity, phase resetting and ERP responses in
