Early ethanol's anxiolytic effects assessed through an unconditional stimulus revaluation procedure

Background: Even though ethanol is considered to exert antianxiety effects, the existence of such properties during early ontogeny of the rat has rarely received attention, mainly because of the restricted behavioral repertoire of the pup. This study evaluated ethanol's anxiolytic properties in preweanling rats through an unconditional stimulus revaluation procedure. Methods: Optimal parameters for the acquisition of an odor avoidance response were obtained in Experiment 1. In Experiment 2 preweanlings experienced 4 conditioning trials defined by a 5 minute exposure to a lemon odor while they were intraorally infused with a sapid aversive stimulus (citric acid). Twenty-four hours later, pups were briefly exposed to the acid 5 minutes after being administered with 0.0, 0.25, 0.5, 1.25, or 2.5 g/kg of ethanol. Odor preferences were then evaluated in a 2-way odor preference test. Blood ethanol concentrations (BEC's) derived from these doses were assessed in Experiment 3. In Experiment 4, citric acid mediated-conditioning was followed by a similar odor-preference test after pups were re-exposed to the acid either 5 or 25 minutes after receiving a 2.5 g/kg ethanol dose. Ethanol's effects upon the avoidance response were also analyzed in an alternative rat strain (Experiment 5). Results: Moderate to low ethanol doses ameliorated the otherwise strong avoidance response. Further experiments: (a) replicated these phenomena, (b) established that they are correlated with BEC's in the range of 17-70 mg%, and (c) Indicated that ethanol's influence upon an avoidance response changes as a function of the temporal course of the intoxication. Conclusions: Acute ethanol interacts with aversive nondrug-mediated learning. These findings are likely to be discussed in terms of possible negative reinforcing properties of ethanol and indicate that this drug exerts differential motivational effects during the course of the intoxication. The devaluation procedure should be considered as an alternative method to assess ethanol's motivational properties.