ABSTRACT
AIM: To study the effects of protein kinase C (PKC) inhibitor, chelerythrine chloride (CH), on nociceptive response, nitric oxide synthase (NOS) expression and nitric oxide (NO) content in spinal cord of rats with inflammatory pain. METHODS: Inflammatory pain was induced by formalin injection into right hind paw. NADPH-d histochemistry was used to investigate the changes of NOS expression. Nitrate/nitrite (NO_2-/NO_3-) was assayed to represent NO content. RESULTS: Compared with the control group, the number of NADPH-d positive cells increased significantly in the superficial layer (LaminaeⅠ-Ⅱ) of the spinal cord dorsal horn and the grey matter surrounding the central canal (Laminae Ⅹ) in rats with inflammatory pain, the reactive degree of NADPH-d positive soma and fibers and NO content of the lumbar enlargement of spinal cord also increased significantly. Intrathecal injection of CH inhibited the spontaneous pain response in the second phase induced by formalin injection, and prevented the increases in the number and reactive degree of NADPH-d positive cells, as well as NO content of the lumbar enlargement of spinal cord. CONCLUSION: It is suggested that the activation of PKC promotes NOS expression and NO production in the nociceptive neurons of spinal cord during formalin-induced inflammatory pain.