Contributions of nitric oxide and prostaglandins to the local increase in muscle blood flow following manual acupuncture in rats.

OBJECTIVE To investigate the contributions of nitric oxide (NO) and prostaglandins (PGs) to the increase in local muscle blood flow (MBF) observed following manual acupuncture (MA). METHODS Male Sprague-Dawley rats (n=112; 250-310 g) were injected intraperitoneally with a non-selective NO synthase inhibitor (NG-nitro-L-arginine methyl ester hydrochloride: L-NAME; 10, 50 or 500 mg/kg), a non-selective cyclo-oxygenase inhibitor (indomethacin; 10, 50 or 500 mg/kg), a combination of L-NAME and indomethacin (500 mg/kg each) or saline only under urethane anaesthesia (1.2 g/kg). We used the sparrow pecking technique for 1 min with a stainless steel acupuncture needle (0.20×30 mm) as the acupuncture stimulation method. The stimulus point was on the right tibialis anterior muscle. (51)Chromium-labelled microspheres were used for MBF measurement. RESULTS MA increased MBF in the saline-injected group (p<0.001). This increase was partially inhibited by L-NAME in a dose-dependent manner (p>0.05, p<0.05 and p<0.001 for 10, 50 and 500 mg/kg, respectively). On the other hand, indomethacin did not suppress the increase (p>0.05 each for 10, 50 and 500 mg/kg). No significant difference was observed between the inhibitory effects of combined administration of L-NAME and indomethacin and single administration of L-NAME (p>0.05). CONCLUSIONS These results suggest that NO is a major factor in the MA-induced increase in MBF, while PGs do not contribute significantly to this increase. As complete inhibition was not achieved by administration of L-NAME±indomethacin, it appears that non-NO and non-PG vasodilators are additionally involved.