Objective      To investigate the effect of environmental noise on the growth and neuropsychological development of newborn rats.       Methods      Sixteen P7 SD rats were randomly divided into a high noise group and a control group (n=8). The mean noise intensities of the high noise group and the control group were 90db (A) and 50db (A)

respectively. The body length and weight of the rats were measured at P10

P15 and P20. The Morris water maze test was applied to observe the learning and memory functions of the rats

ELISA was applied for the detection of growth hormone

and RT-PCR and Western blotting were applied to observe the expression of synaptophysin (SYP) at P20.       Results      The body length and weight of the rats in the high noise group were lower than those in the control group [body length (cm): P10 (9.54±0.1) vs (9.98±0.1)

P15 (10.24±0.1) vs (10.79±0.1) and P20 (10.59±0.1) vs (11.68±0.1); body weight (g): P10 (14.33±0.02) vs (14.51±0.02)

P15 (15.31±0.02) vs (15.68±0.02) and P20 (16.63±0.02) vs (16.76±0.02)

P0.05]. Compared with the control group

the rats of the high noise group showed decreased learning ability

lower level of growth hormone and lower levels of mRNA and protein expressions of SYP [growth hormone (pg/ml): (299.7±4.9) vs (504.9±13.14)

SYP mRNA: (0.182±0.008) vs (1.056±0.011)

and SYP: (0.168±0.007) vs (0.432±0.025)

P0.05].       Conclusion      Slow body length and weight growth and declined learning and memory abilities were observed in newborn SD rats under high noise environment.