Master of Arts (MA)
Faculty of Science
In rats, long daily wheel access produces an escalation to excessive levels of running while short daily access results in low stable levels of running. paralleling patterns of cocaine- taking (Lattanzio et al., 2000). Experiment I explored the effects of previous running experience (Phase l) on ﬁxture running and feeding (Phase ll). Rats with 24 h daily access in Phase I escalated wheel running to a plateau of about 7000 wheel turns per day, while rats with 2 h daily access ran at low levels (about I000 wheel turns over the ﬁnal 8 days of Phase l). The 2 h group did not run the maximum possible. but instead ran approximately one half of the maximum two hour running in the 24 h group. replicating recent ﬁndings. Rats moved from 24 h to 2 h access dropped immediately to the usual running level seen with short access. Their subsequent gradual decrease over Phase ll paralleled Ahmed and Koob's (1999) finding that elevated cocaine use gradually subsides in animals switched from long to short cocaine access. Animals shifted from short to long daily running immediately increased to high levels of running, suggesting that wheel running reward is more salient in these animals. Running plateaus were lower in rats shifted from 0 h to 24 h access. Feeding suppressions were evident in rats increased to long wheel access. Due to the strong circadian pattern of wheel running, Experiment 2 compared running in rats given short wheel access during the light and dark part of the cycle. Running in night-access rats increased steadily over days while the day-access rats’ running remained stable and low. Feeding was suppressed in the night access group only. As with cocaine self-administration, the reinforcing properties of wheel running may have a circadian component. Parallels between wheel running and drug-taking behaviours provide support for the use of wheel running as an animal model of addiction.
Lattanzio, Sara B., "Transition from moderate to excessive wheel running in rats: A function of access length?" (2001). Theses and Dissertations (Comprehensive). 716.