The analgesia induced by intrathecal injection of ruthenium red

Abstract Intrathecally (i.t.) Administered Ruthenium red (40, 80, 160 ng) dose-dependently inhibited formalin-induced nociceptive response. Ruthenium red caused a significant inhibition of pain-related behavioral responses induced by i.t. capsaicin but not by i.t. substance P. These results suggest that ruthenium red produces analgesia by inhibiting the release of neuropeptides in the spinal cord.