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.