Abstract: AIM: To investigate the effect of intrathecal administration of ω-conopeptide SO₃ , a neotype Ntype calcium channel blocker, on the expression of Fos and Jun protein in the spinal cord of a rat model of chronic constriction injury (CCI).METHODS: 72 male SD rats weighing 230 -270 g were randomly divided into nine groups of 8 animals each.After i.t.NS or SO₃ , the animals were perfused intracardially with 4% paraformaldehyde and the L4 -L6 spinal cord section was removed immediately.The changes of Fos and Jun protein expression in the spinal cord were detected by immunohistochemical techniques.RESULTS: The expression of Fos and Jun protein in the spinal cord was minimal in sham operation grouP;CCI induced significant increase in the expression of Fos and Jun protein in both the ipsilateral and the contralateral spinal cords.Acute or chronic i.t.NS had no effect on these expressions.Both acute or chronic i.t.SO₃ significantly inhibited the increase in Fos and Jun protein expression induced by CCI in a dose-dependent manner.CONCLUSION: Upregulation of expression of Fos and Jun protein may be involved in the development of neuropathic pain, and i.t.SO₃ inhibits the increased expression.

Key words: ω-conopeptide SO₃, chronic constriction injury, intrathecal infusion, N-type calcium channel blocker, Fos, Jun