Wheel access in the prior 22 hours is sufficient to reduce d‐methamphetamine self‐administration in rats (661.5)

Initial rat studies appeared to show that an extended, ~6 week interval of activity wheel exposure was needed to reduce intravenous self‐administration of stimulant drugs. Yet a recent study found that ~22hrs of wheel access prior to sessions, without any extended prior exposure, was sufficient to reduce cocaine self‐administration in a between‐groups design. The present study sought to distinguish if the effects of ~22hr wheel access on methamphetamine (MA) self‐administration are an acute or lasting phenomenon using a within subjects design. Groups of male Sprague Dawley rats were trained to stably self‐administer MA (0.05 mg/gk/infusion, i.v.) and then subjected to wheel access/no access conditions when in the vivarium. Intake of MA was significantly lower on sessions following ~22 hrs of access to the wheel compared with sessions which followed ~22 hrs of no‐wheel housing. Effects of the wheel were observed within‐subject in an ABAB design as well as between groups. These data provide evidence that a suppressive effect of wheel activity that had previously been attributed to sustained, multi‐week wheel access is instead due to acute wheel activity in the day prior. Thus, brain plasticity mechanisms that require 6 weeks of chronic activity to produce are unlikely to be related to the suppressive effect of activity on drug self‐administration. This study also has important implications for using exercise as an adjunct to human drug cessation therapy because an extended interval of escalated activity may not be required. Likewise, consistent daily activity may be required for maximum effect. Grant Funding Source : Supported by USPHS Grant DA024105 and DA024705