Effects of special CaMKII inhibitor m-AIP on sensory-discriminative and affective-motivational pain responses in chronic constriction injury of sciatic nerve rats

Abstract

Objective To investigate the sensory-discriminative and affective-motivational pain response of intrathecal injection of m-AIP, a special inhibitor of CaMKII, in a rat model of chronic constriction injury of sciatic nerve(CCI). Methods Eighteen SD rats were divided randomly into 3 groups(n=6): Group S(sham), Group C(control) and Group m-AIP. Group C and m-AIP were operated with the model of neuropathic pain induced by chronic constriction injury of sciatic nerve; Group S were treated as sham operated rats. Seven days after operation, Group S and C received intrathecal injection of 0.9% NaCl 20 μl, while Group m-AIP received intrathecal injection of m-AIP 0.5 nmol/20 μl. Escape/avoidance behavior refrecting the affective-motivational dimension of pain was measured on 1.5 h after administration. Rats received pain behavior tests including paw withdrawal mechanical threshold(PWMT)and paw withdrawal thermal latency(PWTL)before and 2 h, 4 h, 8 h after administration. Results Treatment with m-AIP attenuated escape/avoidance behavior and reversed pain behaviors after CCI. At 2h and 4h after administration, Group m-AIP PWTL((11.45±2.04)s, (10.26±1.48)s) and PWMT((21.15±4.32)g, (20.45±4.09)g) were increased when compared with Group C PWTL((9.63±1.65)s, (9.30±0.73)s), PWMT((13.87±2.36)g, (14.80±3.12)g)(P 0.05). Conclusion CaMKII may play an important role in sensory and affective pain processing in neuropathic rats. Intrathecal injection of m-AIP can effectively improve pain behaviors and attenuate negative affect. Key words: CaMKII; m-AIP; Neuropathic pain; Pain negative affect