Effects of indomethacin and the other anti-inflammatory agents on activation of dorsal horn cell in the spinal cord induced by intra-arterial injection of bradykinin.

Bradykinin (1-2 mug) injected into the femoral artery of the rabbit induced a marked increase in the firing rates of the dorsal horn cells (lamina V cells). This response was markedly inhibited by intravenous administration of indomethacin (1.0 mg/kg), acetylsalicyclic acid (20 mg/kg), aminopyrine (50 mg/kg) and oxyphenbutazone (20 mg/kg) in both intact and spinal preparations. Moreover, the intra-arterial injection of these agents depressed the response in lower doses. With these same low doses, no significant suppression occurred when the intravenous route was used. These results indicate that indomethacin and other anti-inflammatory agents tested suppress the bradykinin-induced response of the dorsal horn cell at the periphery, probably at the paravascular sensory nerve.