Neurotensin is a tridecapeptide, present in the central nervous system and the gastrointestinal tract in man and animals. Previous studies in mice selectively bred for differences in hypnotic sensitivity to ethanol have provided data to suggest that neurotensinergic systems may mediate differences in ethanol's actions in these animals. The present study sought to determine if brain neurotensin levels differed between two lines of rats which have been selectively bred for alcohol preferring or non-preferring behaviors. In addition, electroencephalographic and event-related potential responses to intracerebroventricular saline and neurotensin (10 or 30 microg) were evaluated between the rat lines. Similar to human subjects at high genetic risk for alcoholism, preferring rats were found to have more electroencephalographic fast frequency activity and lowered amplitude of the P3 component of the event-related potential in cortical sites under the saline condition. Overall, electrophysiological response to neurotensin, in the two rats lines, was substantially similar to what has been reported previously in outbred Wistar rats, and consisted of dose-related decreases in overall electroencephalographic spectral power concomitant with increases in amplitude and decreases in the latency of the N1 component of the event-related potential. However, differences in neurotensin responses between the preferring and non-preferring rat lines were also found. The differences in electroencephalographic high-frequency activity and in P3 amplitude seen between the rat lines under control conditions were eliminated by administration of neurotensin. In addition, preferring rats appeared to be more sensitive to neurotensin-induced increases in N1 amplitude. Brain neurotensin concentrations were also found to differ between the lines. Significantly lower concentrations of neurotensin were found in the frontal cortex of preferring rats when compared to non-preferring rats or outbred Wistars. Taken together, these studies suggest that differences in the regulation of neurotensin neurons may contribute to the expression of behavioral preference for ethanol consumption in selective rat lines. Additionally, drugs targeting the neurotensinergic system may plausibly be of utility in the treatment of alcoholism.