Involvement of spinal protein kinase C in induction and maintenance of both persistent spontaneous flinching reflex and contralateral heat hyperalgesia induced by subcutaneous bee venom in the conscious rat

To further study the roles of spinal protein kinase C (PKC) in induction and maintenance of both the persistent spontaneous nociception and the contralateral heat hyperalgesia induced by subcutaneous (s.c.) bee venom injection, the effects of intrathecal (i.t.) treatment with a PKC inhibitor, chelerythrine chloride (CH), were evaluated in conscious rats. Pre-treatment i.t. with CH at three doses of 0.01, 0.1 and 1 nmol produced a dose-dependent suppressive effect on the flinching reflex with the inhibitory rates of 39, 48 and 59%, respectively, when compared with the pre-saline control group. Post-treatment i.t. with the drug at the highest dose used (1 nmol) also resulted in a 42% suppression of the flinching reflex compared with the control. Moreover, pre-treatment i.t. with CH at three doses of 0.01, 0.1 and 1 nmol also produced 12, 22 and 48% inhibition of the contralateral heat hyperalgesia in the pre-saline control group. Post- treatment i.t, with the drug at the highest dose used (1 nmol) also resulted in a 35% reversal effect on the established contralateral heat hyperalgesia. The present result suggests that activation of PKC in the spinal cord contributes to the induction and maintenance of both peripherally-dependent persistent spontaneous pain and contralateral heat hyperalgesia which is dependent upon central sensitization. (C) 2000 Elsevier Science Ireland Ltd. All rights reserved.