Possible Interaction: Carrageenan and Morphine

“ Morphine produced a dose dependent attenuation of carrageenan hyperalgesia but had no effect upon carrageenan inflammation.”

“ Morphine was more potent in decreasing the maximal hyperalgesia induced by carrageenan than that induced by tumor implantation.”

“After the second carrageenan injection, the antinociceptive effects of intraplantar morphine were significantly reduced compared with those obtained after the first carrageenan injection, whereas effects of intravenous morphine were significantly enhanced and present in both hind paws.”

“Results After the first carrageenan injection, intraplantar and intravenous morphine produced significant increase of vocalization thresholds to paw pressure in inflamed but not in noninflamed paws.”

“These experiments suggest that morphine and riluzole attenuate the hyperalgesia induced by injection of carrageenan in the rat hind paw, at least partly, by decreasing glutamate release in the ventral posterolateral thalamic nucleus.”

“Intraplantar morphine (50-200 microg) produced significant elevations of vocalization thresholds to paw pressure in inflamed but not in non-inflamed paws after both carrageenin injection; these effects were reversible by intraplantar naloxone methiodide (40 microg).”

“administration of morphine (3 mg/kg) decreased the total number per section of Fos-Like-Immunoreactive (Fos-LI) neurons by 51%, observed at 2 h after injection of carrageenin.”

“3 Intraplantar morphine dose‐dependently reduced c‐Fos expression induced 1 h 30 min after carrageenin (r = 0.605, P < 0.02), these effects were completely blocked by intraplantar methiodide naloxone (20 μg) (121 ± 22% of control carrageenin expression).”

“4 In the second series of experiments, intraplantar morphine dose‐dependently reduced the number of superficial and deep Fos‐LI neurones induced 3 h after carrageenin (r = 0.794, P < 0.0004 and r = 0.698, P < 0.004, respectively).”

“… morphine dose‐dependently reduced the ankle (r = 0.747, P < 0.… = 0.682, P < 0.005) oedema observed 3 h after carrageenin , with the effect of the highest dose of intraplantar morphine being completely blocked by … naloxone (98 ± 4% and 102 ± 8% of control paw and ankle oedema, respectively).”

“The induction of inflammation resulting from carrageenan injection in the rat hindpaw has been shown to elicit an increase in the antinociceptive potency of morphine , an effect postulated to be related to reduced levels of spinal cholecystokinin (CCK).”

“In addition, morphine reduced the number of deep Fos-LI neurons at 1.5 h and 2 h after carrageenin (86 +/- 4%, P < 0.01 and 82 +/- 8%, P < 0.001 reduction as compared to control carrageenin expression, respectively).”

“In contrast, morphine was less efficacious in decreasing the number of Fos-LI neurons observed in the superficial and deep laminae at 2.5 h after carrageenin (34 +/- 6% and 59 +/- 6% reduction, P < 0.001, respectively).”

“ Systemic morphine did not significantly decrease the number of superficial Fos-LI neurons observed 1 h after carrageenin, whereas it significantly reduced the number of superficial Fos-LI neurons induced at 1.5 h and 2 h after carrageenin (58 +/- 3% and 57 +/- 10% reduction, P < 0.001, respectively).”

“ Morphine inhibited the oedema formation induced by carrageenan.”