Objective  To examine the changes in the plasticity of the large calcium-activated potassium channel α subunit (BKca-α) mRNA and protein in dorsal root ganglion (DRG) neurons and the role it plays in the chronic constriction injury of the

sciatic nerve (CCI).   Methods  Seventy male SD rats weighing 180 to 230 g were randomly divided into 3 groups

control group

sham operation group and CCI group. The sciatic nerve of the right hind leg was exposed without any injury in sham group

but operated according to the methods of Bennett and Xie with slightly improvement in CCI group. Fifty percent paw withdraw thresholds (50% PWML) and radiant heat stimulation (PWTL) were measured before the surgery and in 1

3

7

10

14

17 and 21 d later after sciatic nerve ligation. The DRG of the L

4

to L

6

segments of spinal cord were executed respectively in 7

14 and 21 d after surgery and the expressed variation of the BKca-α mRNA and protein were detected by RT-PCR and Western blotting.   Results  PWTL and PWML were significantly decreased during the 7th to 21st day after CCI as compared to the baseline and sham group. There was no significant difference in BKca-α mRNA and protein expression between the control and sham groups. But the expression was markedly decreased in the surgery groups.   Conclusion  The down-regulation of the mRNA and protein expression of the BKca-α subunit in the DRG neurons may play an important role in neuropathic pain and spinal cord sensitiveness.