Effect of intrathecal dexmedetomidine on expression of cAMP response element-Wnding protein phosphorylation in spinal dorsal horn in a rat model of bone cancer pain

Abstract

Objective To investigate the effect of intrathecal (IT) dexmedetomidine on the expression of cAMP response element-binding protein phosphorylation (p-CREB) in spinal dorsal horn in a rat model of bone cancer pain. Methods Sixty-four adult female Wistar rats weighing 200-240 g were randomly divided into 4 groups (n = 16 each): sham operation group (group S); bone cancer pain group (group BP); normal saline group ( group NS) ; dexmedetomidine group (group D) . Bone cancer pain was induced by injecting Walker 2S6 mammary gland carcinoma cell suspension (2 ×106 cells/ml) 10μl into the medullary cavity of the tibia in BP, NS and D groups. Groups S and BP received no IT injection. Croups NS and D received IT injection of NS 10 μl and dexme detomidine 5 μg/kg respectively 7 days after successful establishment of the model. Ten animals were selected from each group at 1 day before IT administration (T0), immediately before IT administration (T1 ) and at 1, 6, 12 and 24 h after IT administration (T2-5 ) and paw withdrawal threshold (PWT) to mechanical stimuli was measured with von Frey filaments. The other 6 rats in each group were sacrificed at T4 and the spinal cord was removed for determination of p-CREB expression in the spinal dorsal horn.Results PWT was significantly decreased at T1-5 and pCREB expression up-regulated at T4 in BP, NS and D groups compared with group S ( P ＜ 0.05) . Compared with group BP, PWT was significantly decreased at T2-5 and p-CREB expression down-regulated at T4 in group D ( P ＜0.03), while no significant change in PWT and p-CREB expression was found in group NS (P ＞ 0.05) .Conclusion IT dexmedetomidine can reduce the bone cancer pain through inhibiting the phosphorylation of CREB in rat spinal dorsal horn. Key words: Dexmedetomidine; Bone neoplasms; Cyclic AMP response element-binding protein; Spinal cord