Central administration of neuropeptide Y (NPY) in low concentrations has been shown to produce anxiolysis and suppression of locomotor activity, a behavioral profile not dissimilar to that of ethanol. The present study was conducted to ascertain whether NPY and ethanol have similar electrophysiological profiles and to evaluate the combined actions of NPY and ethanol. Eighty-five Wistar rats were stereotaxically implanted with electrodes aimed at dorsal hippocampus, amygdala, and frontal cortex. Rats were administered NPY [or saline (SAL)] intracerebroventricularly (i.c.v.) whereas the doses of alcohol (or SAL) were given intraperitoneally (i.p.). Two doses of alcohol (0.75, 1.5 g/kg) and two doses of NPY (1, 3 nmol) were given alone and in combination. Drug effects were assessed using event related potentials (ERP) recorded in response to an auditory "oddball" plus noise paradigm between 30 and 40 min post-drug. Multivariate analyses of variance (MANOVA) revealed that NPY produced a significant decrease in the amplitude and increase in the latency of the N1 component in cortex and a decrease in the amplitude of the P3 component in amygdala, but no overall effects in hippocampus. Ethanol produced identical effects to NPY on the N1 and P3 components of the ERP in cortex and amygdala. Combined administration of EtOH and NPY (1 nmol) produced effects equivalent to those seen following the higher doses of NPY (3 nmol) or EtOH (1.5 g/kg). These studies demonstrate that NPY and ethanol have a similar electrophysiological profile. In addition, the combined administration of NPY and ethanol produced additive effects.