Objective: To observe the effect of electroacupuncture(EA) on micturition frequency(MF)

and the activity of pontine tyrosine hydroxylase(TH) and vasoactive intestinal peptide(VIP) in the sacral dorsal horn of the spinal cord in L-dopa induced bladder hyperactivity rats so as to investigate its neurobiological mechanism.Methods: A total of 44 female SD rats were randomized into normal(n=6)

saline control(n=10)

model(n=13) and EA(n=15) groups.Bladder hyperactivity model was established by intraperitoneal injection(i.p.i) of Carbidopa((5 mL/kg)) first and L-dopa((5 mL/kg)) 15 min later.Continuous cystometry was performed in conscious rats without any restraint for detecting MF.EA((5 Hz)

4-(6 V)

continuous waves) was applied to bilateral "Zhonglushu"(BL 29) for(30 min).At the end of the experiments

the rats were transcardiacally perfused with 4% paraformaldehyde under deep anesthesia(10% chloral hydrate)

followed by sampling the pons and the sacral cord tissues and cutting into sections ((50 μm and 30 μm respectively)).The activity of TH in pontine tissue and VIP in the sacral dorsal horn of the spinal cord was assayed with immunohistochemical method(ABC method).Results: In comparison with control group

ratios of MF in model group increased significantly(15-45 min)

(46-75 min) and(76-105 min) after injection of L-dopa(P<0.05)

while compared with model group

MF values of EA group declined considerably(4675 min) and(76-105 min) after injection of L-dopa(P<0.05)

suggesting an improvement of L-dopa-induced bladder hyperactivity by EA.Compared with normal group and control group

the relative area values of VIP immunoreaction(IR)-positive fibers and terminals in the sacral cord and TH in pontine tissue increased slightly((3 h)) and significantly((8 h)

(P<0.05)) after i.p i.of L-dopa;while compared with model group

the value of VIP increased notably(3 h) after i.p.i.and those of VIP(8 h) after i.p.i.of L-dopa

and TH(3 h) and(8 h) after i.p.i.of L-dopa decreased markedly((P<0.05))

suggesting that EA could promote the release of VIP from the somatic afferent and inhibit the synthesis of TH in pontine micturition center.Conclusion: EA can inhibit L-dopa induced bladder hyperactivity

raise the VIP activity of sacral cord(3 h) after i.p.i.of L-dopa

and reduce VIP activity(8 h) after i.p.i.and TH activity(3 h) and(8 h) after i.p.i.

which maybe the underlying mechanism of EA in inhibiting bladder hyperactivity by reducing the release of TH from pontine micturition center and promoting the release of VIP from the sacral cord dorsal horn.