PT  - JOURNAL ARTICLE
AU  - SABIH KAYAN
AU  - L. A. WOODS
AU  - C. L. MITCHELL
TI  - MORPHINE-INDUCED HYPERALGESIA IN RATS TESTED ON THE HOT PLATE
DP  - 1971 Jun 01
TA  - Journal of Pharmacology and Experimental Therapeutics
PG  - 509--513
VI  - 177
IP  - 3
4099  - http://jpet.aspetjournals.org/content/177/3/509.short
4100  - http://jpet.aspetjournals.org/content/177/3/509.full
SO  - J Pharmacol Exp Ther1971 Jun 01; 177
AB  - The ability of repeated morphine administration to produce hyperalgesia was studied in rats. The hot plate procedure was used to measure changes in the animal's response latency. The response latency was measured twice at 30-minute intervals, before the injection of the experimental agent and again at 30, 60, 90, 120, 180 and 240 minutes after drug administration. Morphine (5 mg/kg) or saline (2 ml/kg) was given s.c. for varying periods of time. It was found that chronic morphine administration produced hyperalgesia between 60 and 120 minutes after the drug. This hyperalgesia was found not to be the result of a morphine-test interaction. Acute administration of nalorphine, 5 mg/kg, delayed the onset of the hyperahgesic response produced by morphine. Studies designed to delineate the responsible mechanism(s) for this phenomenon may be useful in understanding the analgesic effect of morphine. © 1971 by The Williams & Wilkins Co.