Journal article
Free-running rhythms of cocaine self-administration in rats held under constant lighting conditions
Chronobiology international, Vol.27(3), pp.535-548
05/2010
Handle:
https://hdl.handle.net/2376/107204
PMCID: PMC2933428
PMID: 20524799
Abstract
Using a discrete trials (DT) procedure, we have previously shown that rats exhibit variations in their pattern of cocaine self-administration relative to the time-of-day, often producing a daily rhythm of intake in which the majority of infusions occur during the dark phase of the 24 h light-dark cycle. We have sought to determine if cocaine self-administration demonstrates free-running circadian characteristics under constant-lighting conditions in the absence of external environmental cues. Rats self-administering cocaine (1.5 mg/kg/infusion) under a DT3 procedure (three trials/h) were kept in constant-dim (<2 lux, DIM) conditions, and the pattern of intake was analyzed for free-running behavior. We show that cocaine self-administration has a period length (tau) of 24.14 +/- 0.07 h in standard 12 h light:12 h dark conditions, which is maintained for at least five days in constant-dim conditions. With longer duration DIM exposure, cocaine self-administration free-runs with a tau of approximately 24.92 +/- 0.16 h. Exposure to constant-light conditions (1000 lux, LL) lengthened tau to 26.46 +/- 0.23 h; this was accompanied by a significant decrease in total cocaine self-administered during each period. The pattern of cocaine self-administration, at the dose and availability used in this experiment, is circadian and is likely generated by an endogenous central oscillator. The DT procedure is therefore a useful model to examine the substrates underlying the relationship between circadian rhythms and cocaine intake.
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Details
- Title
- Free-running rhythms of cocaine self-administration in rats held under constant lighting conditions
- Creators
- Caroline E Bass - Department of Physiology and Pharmacology, Wake Forest University Health Sciences, Winston-Salem, North Carolina 27101, USA. cbass@wfubmc.eduHeiko T JansenDavid C S Roberts
- Publication Details
- Chronobiology international, Vol.27(3), pp.535-548
- Academic Unit
- Integrative Physiology and Neuroscience, Department of
- Publisher
- England
- Grant note
- DA023202 / NIDA NIH HHS R01 DA014030-07 / NIDA NIH HHS DA14030 / NIDA NIH HHS DA024763 / NIDA NIH HHS R01 DA023202-03 / NIDA NIH HHS R01 DA023202 / NIDA NIH HHS R01 DA014030 / NIDA NIH HHS K01 DA024763 / NIDA NIH HHS K01 DA024763-02 / NIDA NIH HHS
- Identifiers
- 99900546902201842
- Language
- English
- Resource Type
- Journal article