EEG CHANGES WITH DIFFERENT LEVELS OF MORPHINE SELF-ADMINISTRATION

Authors
Citation
K. Grasing et H. Szeto, EEG CHANGES WITH DIFFERENT LEVELS OF MORPHINE SELF-ADMINISTRATION, Neuropharmacology, 32(6), 1993, pp. 543-553
Citations number
67
Categorie Soggetti
Pharmacology & Pharmacy",Neurosciences
Journal title
ISSN journal
00283908
Volume
32
Issue
6
Year of publication
1993
Pages
543 - 553
Database
ISI
SICI code
0028-3908(1993)32:6<543:ECWDLO>2.0.ZU;2-C
Abstract
Rats with chronically implanted jugular catheters and cortical EEG ele ctrodes were allowed 24 hr per day access to morphine infusions (30 mu g/kg) contingent on lever-pressing. Yoked control subjects received th e same number and pattern of infusions as contingent subjects in an ad jacent cage. Six subjects were studied, with data analyzed over 84 day s of contingent and 63 days of yoked control (noncontingent) treatment . Self-administration rates were positively correlated with previous e xposure to morphine. EEG total power was reduced in both contingent an d yoked subjects during periods of self-administration. Averaging of t rends in EEG power over time across multiple episodes of self-administ ration showed a greater reduction in power for contingent subjects tha t preceded the majority of morphine infusions. Desynchronization (dimi nished EEG amplitude) for contingent subjects at the onset of self-adm inistration is probably related to lever-pressing activity. Ultradian describes biological rhythms in which the duration of one cycle (perio d) ranges from several minutes to values less than 24 hr. In both cont ingent and yoked subjects at intermediate or high levels of self-admin istration, increases occurred in the period and amplitude of ultradian cycles in EEG total power. Responsiveness to the light-dark cycle was also diminished at these levels of self-administration. In conclusion , morphine self-administration at intermediate or high levels disrupts both diurnal and ultradian rhythms in EEG total power for both contin gent and yoked subjects. The ultradian EEG pattern associated with gre ater levels of morphine self-administration resembles diminished varia tion in EEG power that occurs normally during the inactive rest phase of the diurnal cycle.