Objective To observe the effect of perpendicular and subcutaneous transverse needling at "Sanyinjiao"(SP6) on visceral pain behavior

arginine vasopressin(AVP) content in the serum

uterine tissues

spinal cord and hypothalamus and expression of AVP receptors AVPR1 A and AVPR1 B in the uterine tissues

spinal cord and hypothalamus in cold-stasis(stasis due to pathogenic cold) type dysmenorrhea rats

so as to explore their mechanisms underlying pain relief. Methods Forty female SD rats were randomly divided into blank control

model

perpendicular needling and transverse needling groups

with 10 rats in each group. The cold-stasis dysmenorrhea rat model was established by exposure in a freezer(-25 ℃) for 4 h

once daily for 5 days

and subcutaneous injection of estradiol benzoate(once daily for 10 days) and intra-abdominal injection of oxytocin injection(once). For rats of the two acupuncture groups

acupuncture needles were inserted into the bilateral SP6 perpendicularly or transversely to a depth of about 4-5 mm

and retained for 20 min. The abdominal pain behavior was assessed by recording the writhing latency and scaling the rats' writhing reactions after modeling. The contents of AVP in the serum

uterus

spinal cord and hypothalamus tissues were assayed using ELISA and the expression of AVPR1 A and AVPR1 B in the uterus

spinal cord and hypothalamus was measured by using Western blot and quantitative real time-PCR

respectively. Results After mode-ling and compared with the blank control group

the writhing latency was significantly shortened(P<0.05)

and the writhing score in the first 20 min was significantly increased(P<0.01) in the model group. After the intervention

the writhing latency was significantly prolonged(P<0.01)

and the writhing scores in 20 min were significantly decreased(P<0.01) in the two needling groups. The AVP contents were obviously increased in the serum and uterine tissue(P<0.05

P<0.01) but decreased appa-rently in the spinal cord and hypothalamus tissues(P<0.01

P<0.05)

and the expression levels of AVPR1 A or AVPR1 B protein and mRNA were markedly increased in the uterine tissues(P<0.01

P<0.05)

and significantly decreased in the spinal cord and hypotha-lamus in the model group relevant to the control group(P<0.05

P<0.01). Following the intervention

The AVP content in the serum of the perpendicular needling group(P<0.05) and that in the uterus of the two needling groups were significantly decreased(P<0.01)

as well as that in the hypothalamus was obviously increased in the two needling groups(P<0.05). The expression levels of AVPR1 A protein and mRNA in the uterus were significantly down-regulated in the two needling groups(P<0.01

P<0.05) and AVPR1 B protein in the hypothalamus of the perpendicular needling group was up-regulated(P<0.05). Moreover

no significant differences were found between the two needling groups in regulating the related indexes mentioned above(P>0.05).Conclusion Both perpendicular and subcutaneous transverse needling at SP6 have an immediate analgesic effect in cold-stasis type dysmenorrhea rats

which may be related to their effects in regulating AVP levels and its receptor expression in the uterine and hypothalamus.