ABSTRACT
Objective To study the influence and dose effect of ultrasound on the contraction of uterine smooth muscle in rats.Methods Estradiol benzoate was injected into rats three days before conducting an in-vitro experiment.Their uteri were resected and irradiated with ultrasound(0.8 MHz,3 W/cm~2,0-40 rain).The contrac- tion frequency and amplitude were recorded using an MS-302 biological experiment system.Results It could be seen that the contraction frequency and amplitude,and general contractile activity were significantly increased during ultrasonic irradiation(P＜0.01).The increased contraction frequency and amplitude lasted for ten minutes,and then the normal contraction pattern resumed.The contraction frequency as well as the percentage change in eontraction fre- quency were highest during the first 15 minutes of ultrasonic irradiation;the contraction amplitude as well as the per- centage change in amplitude were highest during 40 minutes of ultrasonic irradiation.Contraction activity was at its highest for 30 minutes,but the percentage change in activity was highest for 20 minutes.Conclusions Ultrasound can induce uterine smooth muscle contraction in rats.This biological effect is related to the irradiation time.