Abstract:Aim:Formalin test was used to examine the role of Chlorpromazine in hyperalgesia induced by tissue injury. Methods and Results: An early and a late response (hyperalgesia) of pain are produced by subcutaneous injection of formalin in one paw of rats. The late response is significantly reduced by a PKC inhibitor, Chlorpromazine. It is suggested that PKC might play an important role in pain process and its central sensitization.