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Related Experiment Videos

EEG changes with different levels of morphine self-administration

K Grasing1, H Szeto

  • 1Department of Pharmacology, Cornell University Medical College, New York, NY 10021.

Neuropharmacology
|June 1, 1993
PubMed
Summary

Morphine self-administration disrupts natural biological rhythms in rats, altering both daily (diurnal) and shorter (ultradian) EEG power cycles. These disruptions are linked to lever-pressing activity and morphine exposure levels.

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Area of Science:

  • Neuroscience
  • Pharmacology
  • Chronobiology

Background:

  • Opioid self-administration can alter physiological processes.
  • Understanding the impact of drug-seeking behavior on biological rhythms is crucial.

Purpose of the Study:

  • To investigate the effects of chronic morphine self-administration on EEG power and ultradian rhythms in rats.
  • To differentiate between effects of active drug-seeking and passive drug exposure.

Main Methods:

  • Rats underwent chronic implantation of jugular catheters and EEG electrodes.
  • Subjects self-administered morphine (30 µg/kg) contingent on lever-pressing, with yoked controls receiving non-contingent infusions.
  • EEG total power was analyzed over 84 days of contingent and 63 days of yoked treatment.

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Main Results:

  • Self-administration rates correlated positively with prior morphine exposure.
  • EEG total power decreased during self-administration in both groups, with greater reduction preceding infusions in contingent subjects.
  • Ultradian rhythm period and amplitude increased, and light-dark cycle responsiveness diminished at higher self-administration levels.

Conclusions:

  • Chronic morphine self-administration disrupts diurnal and ultradian EEG power rhythms in rats.
  • Observed ultradian EEG patterns during high morphine intake resemble normal variations during rest phases.