Withdrawal from chronic morphine administration causes prolonged enhancement of immobility in rat forced swimming test
by
Anraku T, Ikegaya Y, Matsuki N, Nishiyama N.
Laboratory of Chemical Pharmacology,
Graduate School of Pharmaceutical Sciences,
University of Tokyo, Japan.
Psychopharmacology (Berl) 2001 Sep;157(2):217-20

ABSTRACT

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.

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