[Effect of electroacupuncture of different acupoints on the excitability of detrusor muscle and the expression of BDNF and TrkB in the spinal cord of rats with urinary retention due to spinal cord injury].

Objective: To observe the effect of electroacupuncture (EA) of different acupoints on the expression of brain-derived neurotrophic factor (BDNF) and tropomyosine receptor kinase B (TrkB) in the spinal cord and the excitability of detrusor muscle of the uninary bladder in rats with urinary retention owing to spinal cord injury (SCI).

Methods: A total of 100 female SD rats were randomly divided into normal, sham-operation (sham), model, EA-Guanyuan (CV 4), and EA-Shuidao (ST 28) groups, with 20 cases in each. SCI induced urinary retention model was established by using weight dropping method. EA (1 mA, 2 Hz/15 Hz) was applied to "Guanyuan" (CV 4) and "Shuidao" (ST 28) respectively for 20 min, once a day for 10 days. The excitability (tone, contraction frequency) of the detrusor muscle of the bladder was detected in vitro by using electrophysiological method, and the expression of BDNF and TrkB in spinal cord was determined by immunohistochemistry staining.

Results: In comparison with normal control and sham groups, the tension and the contraction frequency of detrusor muscle in model group lowered significantly (P<0.05), while compared with model group, both the tension and contraction frequency of detrusor muscle increased pronouncedly in EA-CV 4 and EA-ST 28 groups (P<0.05), and the effect of EA-CV 4 was apparently superior to that of EA-ST 28 (P<0.05). In comparison with normal and sham groups, the BDNF and TrkB immunoreaction positive cells in the spinal cord were significantly more in model group (P<0.05). Compared with model group, those of EA-CV 4 and EA-ST 28 groups were obviously further increased (P<0.05), and the effect of EA-CV 4 group was markedly superior to that of EA-ST 28 group (P<0.05).

Conclusion: EA of CV 4 and ST 28 can raise the excitability of the smooth muscle of the uninary bladder in rats with SCI-induced urinary retention, which may be related to its effects in upregulating the expression of BDNF and TrkB in the spinal cord. The effects of EA of CV 4 were evidently superior to those of EA of ST 28.