Master of Science (MSc)
Faculty of Science
Two experiments were conducted to determine whether cross-sensitization/tolerance between wheel running and the drugs amphetamine and morphine is possible in male Sprague Dawley rats. Each experiment compared a non-wheel control group and a chronic wheel access group of rats. Following a 24 day period of wheel access all animals were presented with a drug and saline challenge test (counterbalanced) with either 1 mg/kg of amphetamine (Experiment 1) or 10mg/kg or morphine (Experiment 2). Prior to the challenge tests all animals were habituated to the novel testing environment in two 1 hr sessions (Experiment 1) or one 2 hr session (Experiment 2) to attenuate the acute motoric response to a novel environment. Behavioral sensitization/tolerance was measured by locomotion (cm) within long narrow activity boxes with the Ethnovision video tracking system. In the first experiment the wheel access rats were significantly more active during the 1 hr amphetamine challenge test than the non-wheel rats thus showing sensitization. In Experiment 2, the wheel access rats demonstrated a reduced hypoactivity in the first hour and an augmented hyperactivity in the second hour of the 2 hour drug challenge test in comparison to the non-wheel rats after morphine administration thus showing both tolerance and sensitization. These two experiments provide strong support that cross-sensitization and cross-tolerance exists between wheel-running and amphetamine or morphine in rats. In both experiments the final level of wheel running, which varied greatly, was not correlated with the degree of cross-sensitization/tolerance to either amphetamine or morphine suggesting that the changes induced by wheel running were similar in all animals. In Experiment 2 it was also found that levels of both initial and final levels of wheel running were uncorrelated with a prior 2 hour baseline locomotor activity test suggesting that an enhanced vulnerability to the addicting behavior of wheel running could not be demonstrated by looking at the level of wheel running in rats.
Inkster, Clint, "Cross-sensitization/tolerance between wheel running and amphetamine and morphine in rats" (2006). Theses and Dissertations (Comprehensive). 785.