Conditioned alcohol cues produce craving and may contribute to relapse. These effects of alcohol cues may be related to their functioning as: 1) conditioned reinforcers [they maintain behavior that produces contact with them], and 2) motivators of drinking [contacting them makes drinking more likely]. The endogenous opioid system mediates the reinforcing effects of alcohol and is related to genetic susceptibilities to alcoholism. Little research has focused on the role of the opioid system in the conditioned reinforcing and motivating effects of alcohol cues. We recently developed a procedure (the observing-response procedure) that avoids many problems with other animal models of the conditioned reinforcing effects of alcohol cues, but have not yet examined the motivational impact of the alcohol cues on drinking. The utility of this procedure for examining the neuropharmacological mechanisms of alcohol cues is also unknown. This research has three specific aims. First, we aim to examine the motivating effects of the alcohol cues in the this procedure by examining their impact on the sensitivity of alcohol drinking to increases in the cost of alcohol. In Exp.1 rats will self-administer alcohol across increasing costs (work per unit alcohol) and sensitivity to price will be examined when alcohol cues are available or unavailable.
Our second aim i s to examine how opioid antagonism affects sensitivity of drinking and responding for alcohol cues to increases in the cost of alcohol. Exp. 2 examines the effects of naltrexone on drinking and responding for alcohol cues in the observing-response procedure.
The third aim i s to determine if the effects of naltrexone interact with availability of conditioned alcohol cues. Exp. 3 examines this interaction with a subset of prices and naltrexone doses determined in Exp.1 and Exp. 2. This experiment will determine if any decreases in alcohol consumption produced by opioid antagonism are affected by the motivating effects of alcohol cues. The further development and evaluation of these methods is important for the continued growth of our understanding of alcohol cues and their role in craving and relapse. By using the observing-response procedure we may be better able to decrease their impact on people being treated for alcoholism. Future studies could examine the role of specific opioid receptor subtypes or other receptor systems in the effects of alcohol cues and their relationship to genetic susceptibility to alcoholism.
