Effects of Morphine on Oedema and Tissue Concentration of Nerve Growth Factor in Experimental Inflammation of the Rat Paw

Abstract

Injection of carrageenan (1 mg) into the rat hind paw caused a time-dependent increase in paw volume that was maximal 3 h after injection. At this time, the concentration of nerve growth factor (NGF) in the skin of the inflamed paw was more than twofold higher than in the contralateral, non-inflamed paw. Treatment of rats with indomethacin reduced inflammatory oedema by 57%, morphine treatment attenuated oedema by 62%. While indomethacin had no statistically significant effect on the concentration of NGF in the skin of inflamed paws, morphine attenuated the NGF response by 24.2% in a naloxone reversible manner. These data suggest that drug-induced inhibition of inflammatory oedema is not predictive of its effect on an inflammation-induced rise in tissue NGF. Furthermore, our results confirm and extend previous observations suggesting an anti-inflammatory activity of morphine.