THE EFFECT OF COCAINE ON DELAY DISCOUNTING IN THE SPONTANEOUSLY HYPERTENSIVE RAT
Perhaps the most controversial and adverse side effect of long-term cocaine use is increased impulsivity which is seen in human and animal models (Moeller et al., 2001; Simon, Mendez, & Setlow, 2007). Impulsivity is behaviorally defined as picking a smaller, immediate reward (impulsive choice) over a larger, later reward (self-control choice). Currently, researchers hypothesize that the interaction between mesocortocolimbic structures and the dorsal striatum are what mediate this impulsive decision making (Belin & Everitt, 2008). An identical preference for the smaller sooner reward can be seen within ADHD, and is known as delay aversion (Sonuga-Barke, 2003). In animals, the spontaneously hypertensive rat (SHR) is the most widely used model of ADHD. In various research projects the SHR has shown some of the major behavioral symptoms of ADHD (Sagvolden, 2000). However, many researchers are beginning to refute its use as an animal model of ADHD (Alsop, 2006). Therefore, the present study examines the effects of acute cocaine administration on impulsive behavior in the SHR, implementing a pre-test and post-test experimental design. Four Sprague Dawley and five SHR rats were sensitized to cocaine HCl for 14 days at a dosage of 30 mg/kg through intraperitoneal injections. Following cocaine sensitization was an intermediate period for 28 days where the rats were housed in cages. Through the use of an adjusting amount procedure pioneered by Green et al., (2004) we calculated indifference points for each rat. Our results demonstrated that the SHR was no more impulsive than the Sprague Dawley, and that neither strain had differential impulsivity after cocaine sensitization. These results suggest that the SHR is not a completely functional animal model of ADHD. Additionally, this project investigates the neurobiological differences of the SHR and the Sprague Dawley using immunohistochemistry, staining for the dopamine transporter in the dorsal striatum.
Additional Abstract Information
Student(s): Matthew M. Clasen, Sancho N. Sequiera
Department: Psychology
Faculty Advisor: Dr. Jeffrey A, Dyche, Dr. Catherine L. Franssen, & Dr. Daniel D. Holt
Type: Poster
Year: 2014
