[Effect of Electroacupuncture at Distal and Proximal Acupoints on Expression of Spinal p 38 Mitogen-activated Protein Kinase and Cyclic Adenosine 3',5'-monophosphate in Rats with Lumbago].

Objective: To observe the influence of Electroacupuncture (EA) stimulation of different distal-proximal acupoints combination groups on pain reaction, spinal p 38 mitogen-activated protein kinase (p 38 MAPK) expression and cyclic adenosine 3', 5'-monophosphate (cAMP) content in experimental lumbago rats.

Methods: Seventy-eight male SD rats were randomized into normal, model, sham operation, EX-B 2-BL 25 (proximal acupoints, PA), BL 40-BL 60 (distal acupoints, DA) and DA+PA groups. The lumbago model was established by implanting the autologous nucleus pulposus to the site close to the left L 5 dorsal root ganglion and the surface of dura mate of spinal cord. EA (2 Hz/100 HZ,1-3 mA) was applied at bilateral EX-B 2-BL 25 or BL 40-BL 60 or both for 20 minutes, once daily for 7 days. The mechanical pain threshold was measured, and the expression of p 38 MAPK in the lumbar spinal cord was detected by immunohistochemistry and Western blot, separately. The content of cAMP in spinal cord (L 4-L 6) was measured by enzyme-linked immunosorbent assay (ELISA).

Results: After mode-ling, the mechanical pain threshold percentages were significantly decreased on day 3, 5 and 7 (<0.01), and after EA stimulation of DA,PA and DA+PA, the decreased pain threshold was significantly increased at the 3 time-points (<0.01), and the effects of both PA and DA+PA were markedly superior to that of DA (<0.05, <0.01). Following modeling, lumbar spinal p 38 MAPK immunoactivity and protein expression, and cAMP content were obviously up-regulated (<0.01). Compared with the model group, the levels of p 38 MAPK immunoactivity and protein expression in the 3 EA groups and the sham group, and cAMP contents in both PA and DA+PA groups (not in the DA and sham groups) were considerably down-regulated (<0.01, <0.05).

Conclusions: EA stimulation of distal+proximal acupoints and proximal acupoints near the focus can raise pain threshold in lumbago rats, which may be associated with their effects in suppressing lumbago-induced increase of expression of spinal p 38 MAPK protein and cAMP content. The effects of EA of distal+proximal acupoints and proximal acupoints are better than those of EA of simple distal acupoints.