Two groups of naive, male, albino rats derived from different genetic strains (Sprague-Dawley and Wistar) were given a 5 μg/ml etonitazene solutions 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.
Bibliographical noteFunding Information:
This research was supported by NIDA grants DA 03240 and DA 00944
- Food deprivation
- Food satiation
- Genetic differences in drug intake