Parameters of low-dose ethanol intravenous self-administration in the rat.

Male Wistar rats were able to press on an operant lever 24 hr/day for intravenous infusions of saline or ethanol at doses of 0.5, 1.0 or 5.0 mg/kg/infusion. Only the 1.0 mg/kg/infusion group showed a significant increase in responding on the lever as a function of days, whereas the 5.0 mg/kg/infusion group showed a significant decrease in responding as a function of days. The results suggest that the reinforcing value of intravenous ethanol changes from rewarding to neutral or aversive in valence at dose-level below that expected to produce signs of intoxication.