2. A role for DA Mechanisms in the ovBNST in Compulsive Responding in Rats

Abstract

Out of the primary characteristics of drug addiction, compulsive drug seeking and intake is perhaps the most insidious, as it results in voluntary substance use despite negative physical and social consequences. For substances that are not considered classically addictive, such as sucrose, animal models of drug addiction may be utilized to explore reward-related synaptic changes underlying compulsive behavior similarly observed in binge eating disorders. Binge eaters, like those who compulsively seek out and consume drugs, continue to consume food despite the negative consequences. Based on previous work done by Maracle (2012), we examined the effects of modulating signalling in the oval bed nucleus of the stria terminalis (ovBNST) with a competitive D1 antagonist and its effects on compulsive intake. Prior to the intermitted access phase, subjects (N=66) underwent intracranial surgeries targeting the ovBNST. We utilized the same intermitted access cycle developed by (Avena, 2010). The subjects were randomly assigned to one of the four groups, 12-hr sucrose (primary experimental group),12-hr saccharine (sweet taste control group), 12-hr food only group, and a 24-hr sucrose/food group. After the 28-day cycle, subjects were then randomly assigned to received infusions of either saline or a selective D1 antagonist (SCH 23390) 10mins prior to testing. Compulsive responding for sucrose was then assessed using a conditioned suppression paradigm. It was hypothesized that infusing a DA antagonist into the ovBNST will decrease compulsive responding in subjects who demonstrate bingeing behaviour during the intermitted access phase, but will not affect animals that do not demonstrate bingeing behavior.