Role of dopaminergic receptors in acute joint inflammation in the rabbits

  The dopaminergic system has different effects on the cardiovascular and immune systems. Since both vascular injuries and activation of the immune system are involved in joint inflammation, in the present study the role of dopaminergic receptors in knee joint inflammation was studied. Evans blue (75 µ g/kg) was used in order to observe changes in permeability which occurred during the process of inflammation. Inflammation was induced by injection of 1 ml kaolin (4 %) into the knee joint of the rabbit. This process was studied on different hours (2, 4, 8 and 24). Maximum inflammation was achieved after 4 hours. SKF38393, a Dl agonist, reduced knee joint inflammation. This response was dose-dependent. Also, injection of SCH23390, a Dl antagonist, prior to SKF38393 injection, attenuated its effects dose-dependently. Using SCH23390 per se did not affect the kaolin-induced inflammation. In another group, nifedipine, a calcium channel blocker, reduced the anti-inflammatory effect of SKF38393. The effects of LY171555, a D2 agonist, and sulpiride, a D2 antagonist, were also studied, and no significant changes were observed.