[Effect of moxibustion of "dachangshu" (BL 25) area on pain reaction and TRPV 1 mRNA expression of bone marrow cells in visceral hyperalgesia rats].

Objective: To observe the effect of moxibustion of "Dachangshu" (BL 25) on pain reaction and expression of transient receptor potential vanilloid 1 (TRPV 1) of bone marrow cells in visceral hyperalgesia (VHA) rats so as to explore its mechanism underlying visceral pain-relief.

Methods: Twenty-eight male SD rats were divided into control group, control+moxibustion group, VHA model and VHA+moxibustion group (n = 7/group). The VHA model was made by giving colorectal distension (CRD, 60 mmHg) to the newborn rats for 1 min (repeated once again in 30 min) from postnatal day 8 on, once daily for a week. Moxibustion was applied to ipsilateral "Dachangshu"(BL 25) area for 40 min from the 8th week on after birth. Abdominal withdrawal reflex (AWR) and pain threshold during CRD were measured before and after moxibustion. The TRPV 1 mRNA expressio of bone marrow cells was detected by real time-POR.

Results: (1) The AWR score of the model group was significantly higher than that of the control group, but the pain threshold of the model group was significantly lower than that of the control group (P < 0.01), suggesting a VHA in model rats. (2) After moxibustion, the AWR scores were significantly lower in the VHA+moxibustion group than in the model group (P < 0.05, P < 0.01), and the pain threshold was remarkably higher in the former group than in the latter group (P < 0.01). Similar results were found in the control+moxibustion group compared to the control group: the decreased AWR scores (CRD 40 mmHg, 60 mmHg and 80 mmHg, P < 0.01) and the increased pain threshold (P < 0.05). (3) The TRPV 1 mRNA expression level of bone marrow cells was significantly lower in the VHA + moxibustion group than in the model group (P < 0.01). No significant difference was found between the control and moxibustion+control groups in TRPV 1 mRNA expression level (P > 0.05).

Conclusion: Moxibustion of "Dachangshu" (BL 25) can reduce visceral hyperalgesia and down-regulate TRPV 1 mRNA expression of bone marrow cells in VHA rats, suggesting an involvement of TRPV 1 mRNA of bone marrow cells in CRD-induced visceral pain development.