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Withdrawal from chronic morphine administration causes prolonged enhancement of immobility in rat forced swimming
T Anraku1, Y Ikegaya, N Matsuki
1Laboratory of Chemical Pharmacology, Graduate School of Pharmaceutical Sciences, University of Tokyo, Japan.
Rationale:
Opiate-dependent subjects experience severe depression as one of the subjective symptoms during withdrawal. No experimental work, however, has focused on the ability of opiate-withdrawal to produce depression-like behavior in dependent animal. OBJECTIVES. We therefore investigated whether withdrawal from chronic morphine treatment affects immobility in forced swimming test in rats.
Methods:
Morphine was administered in a dose escalation fashion using doses ranging from 20 to 140 mg/kg twice daily for 14 days, followed by 1-6 days of withdrawal, and their duration of immobility was assessed.
Results:
After the last morphine treatment. an increase in immobility occurred late on day 3 and persisted to at least day 6 of withdrawal without any change in ambulatory activity.
Conclusions:
The results suggest that the morphine withdrawal resulted in prolonged enhancement of depression-like behavior in drug-dependent laboratory animals.
