Two groups of naive, male, albino rats derived from different genetic strains (Sprague-Dawley and Wistar) were given a 5 micrograms/ml
etonitazene solution as their only available liquid. Liquid intake and
body weights were recorded every 24 hr.
Etonitazene intake was compared to baseline water intake, and
drug intake was then compared when the rats were food deprived (25 sessions) and food satiated (24 sessions). Both groups drank similar amounts of water and
etonitazene during the initial food satiation phase, although
drug intake was slightly below water intake. When they were food deprived, the Wistar group's mean
etonitazene intake almost doubled, while the Sprague-Dawley group's
drug intake decreased by nearly 50%. The
etonitazene intake in the Sprague-Dawley group never exceeded that of the vehicle, water; thus, it appeared that the
drug was not functioning as a reinforcer. Food deprivation increased
etonitazene intake above water levels in the Wistar group, indicating that the
drug was serving as a reinforcer. Both groups showed similar
drug effects during food deprivation, such as erratic drinking patterns,
self-mutilation and other forms of stereotypy. Thus, both strains were sensitive to
etonitazene's effects; they appeared to differ only with respect to the reinforcing effects. These results suggest that genetically-based differences in the reinforcing effects of drugs may be revealed by food deprivation.