[Effect of noise on blood pressure of various types of rats]

Before the experiment, male Wistar rats were divided into two types (A and B) according to the different responses of their ECG and Heart Rate (HR) to 1 hour noise exposure: in type A, the ST segment elevated and HR decreased significantly during the exposure; in type B, both ST segment and HR showed no considerable variation. We exposed type A and B wistar rats and spontaneously hypertensive rats (SHRs) of 105 dB steady-state noise, 4 hours per day, 6 days per week. The results showed that after 3 weeks of noise exposure, the mean systolic blood pressure (BP) of type A rats was significantly higher than that of type B and control rats. This higher BP retained progressively till the end of observation (35 weeks); while there were not significant changes of BP in type B rats during the period of 35 weeks noise exposure. We also found that when exposed to noise for 14 weeks, the SHRs in exposure group had markedly higher mean systolic BP than those in control group. The results indicated that noise may affect BP of both Wistar rats and SHRs. There is probably a difference in the susceptibility of BP response to noise. The susceptibility of the BP of rats in type A to noise is greater than that of rats in type B.