Objective To observe the effect of twirling-reinforcing or reducing needling manipulations on plasma acetylcholine(Ach)content and expression of nitric oxide synthetase(NOS)and cyclic guanosine monophosphate(cGMP)in thoracic artery tissue in stress-induced hypertension rats.Methods A total of 60 male rats were randomly divided into blank control

model

acupuncture(no-needle-manipulation)

twirling-reinforcing needling and twirling-reducing needling groups(n=12in each group).The stress hypertension model was established by giving the animals with noise and electric shock stimulation(paw)

twice a day for15 days.Acupuncture stimulation was applied to bilateral"Taichong"(LR 3)for 1min

followed by retaining the needles for 20 min.The treatment was conducted once daily for 7days.Systolic blood pressure of the rat's tail was detected with non-invasive method and plasma Ach

and NOS and cGMP contents in the thoracic artery tissue were measured using ELISA method.Results Compared with the control group

the systolic blood pressure was significantly higher in the model group after 15days' stress stimulation(P<0.01)

while the contents of plasma Ach

arterial NOS and cGMP were markedly down-regulated(P<0.01).Following 7days' acupuncture interventions

the increased blood pressure was down-regulated in the no-needle-manipulation

twirling-reinforcing needling and twirling-reducing needling groups(P<0.05

P<0.01);and the decreased Ach and NOS in the 3treatment groups

and cGMP levels in the twirling-reinforcing and twirling-reducing needling groups were remarkably up-regulated(P<0.01

P<0.05).No significant change of arterial cGMP content was found in the no-needle-manipulation group(P>0.05).The effect of the twirling-reducing needling was superior to that of no-needle-manipulation and twirling-reinforcing needling in lowering blood pressure and raising plasma Ach content(P<0.05

P<0.01).Conclusion The twirling-reducing needling of acupuncture has a significant anti-hypertensive effect in stress hypertension rats

which may be associated with its effects in raising blood Ach

and arterial NOS and cGMP levels.