Objective      To observe the effect of low-frequency ultrasound therapy on healing time and the contents of NO and NO synthetase (NOS) in ulcer tissues of rat models with oral mucosal ulcer.       Methods      Thirty-six Sprague-Dawley (SD) rats were randomly divided into six groups

including a normal control group

a model group

a 1% iodine glycerin group and three low-frequency ultrasound groups (with different energy levels of 1.1 W

1. 58 W and 2.06 W

respectively). Except for the normal control group

the rats of the other five groups were given oxygen free radicals and physical burn to construct the oral mucosal ulcer models. At 24 h after last treatment

three rats of each group were sacrificed and the cheek pouches were obtained for the detection of NO and NOS contents in the mucosal tissues by spectrophotometry. The ulcer healing was also observed for 8 consecutive days. The efficiency of low-frequency ultrasound therapy with different energy levels was evaluated.       Results      The healing time of the low-frequency ultrasound groups was shorter than that of the model group and 1% iodine glycerin group. The contents of NO and NOS in the low-frequency ultrasound groups (NO: 9.86±1.69

9.42±1.34 and 8.51±1.26 μmol/g; NOS: 3.89±0.72

4.35±0.53 and 4.74±0.81 μmol/g) were significantly lower than those in the model group (NO: 23.85±4.81 μmol/g; NOS: 6.48±0.77 μmol/g) (P0.05)

but were not significantly different from those in the normal control group (NO: 10.88±1.68 μmol/g; NOS: 3.83±0.99 μmol/g

P0.05).       Conclusion      Low-frequency ultrasound therapy with appropriate energy levels can effectively reduce the contents of NO and NOS in ulcer tissues

and can promote the process of ulcer healing.