Rationale: Operant self-administration (SA) is an important model of motivation to consume ethanol (EtOH), but low rates of voluntary consumption in rats are thought to necessitate water deprivation and saccharin/sucrose fading for acquisition of responding.
Objectives: Here, we sought to devise an effective model of SA that does not use water deprivation or saccharin/sucrose fading.
Methods: First, we tested if Wistar rats would acquire and maintain SA behavior of 20 % EtOH under two conditions, water deprivation (WD) and non-water deprivation (NWD). Second, we tested the efficacy of our SA procedure by confirming a prior study which found that the NK1 antagonist L822429 specifically blocked stress-induced reinstatement of EtOH seeking but not SA. Finally, we assessed the effect of naltrexone, an FDA-approved medication for alcohol dependence that has been shown to suppress EtOH SA in rodents.
Results: Lever presses (LPs) and rewards were consistent with previous reports that utilized WD and saccharin/sucrose fading. Similar to previous findings, we found that L822429 blocked stress-induced reinstatement but not baseline SA of 20 % EtOH. Moreover, naltrexone dose-dependently decreased alcohol intake and motivation to consume alcohol for rats that are self-administering 20 % EtOH.
Conclusions: Our findings provide a method for voluntary oral EtOH SA in rats that is convenient for experimenters and eliminates the potential confound of sweeteners in EtOH-operant SA studies. Unlike models that use intermittent access to 20 % EtOH, this method does not induce escalation, and based on pharmacological experiments, it appears to be driven by the positive reinforcing effects of EtOH.