Stein C, Millan M J, Yassouridis A, Herz A
Department of Neuropharmacology, Max-Planck-Institut für Psychiatrie, München, F.R.G.
Eur J Pharmacol. 1988 Oct 18;155(3):255-64. doi: 10.1016/0014-2999(88)90511-0.
Rats received an injection of Freund's complete adjuvant into the right hindpaw and developed localized inflammation. Four to six days after inoculation, the antinociceptive effect of both the mu-agonist, morphine, and the kappa-agonist U-50,488H, administered subcutaneously, was markedly enhanced in the inflamed paws. This effect was dose dependently antagonized by low dose of intraplantar, but not subcutaneous or intravenous, (-)-naloxone. (+)-Naloxone was inactive. These data indicate that the enhanced antinociceptive effects of both agonists in inflammation are mediated by a peripheral, opioid receptor-specific mechanism.
