To study the possible effect of the transformer noise exposure below 65 d B

as A weighting sound pressure level

on the neurotransmitter and nervoustissue in hippocampus of SD rats

we experimentally investigated the transformer noise in a 1 000 k V UHV substation

as noise experiment source. The noise samples were replayed in the noiseproof box. 96 SD rats were grouped randomly into noise exposed group S1（32）

S2（32）

and control group C（32）. The noise exposed group S1 was exposed to the 60 d B and the exposed group S2 was exposed to the 65 d B transformer noise for consecutively 35 days

the transformer noise was diurnal equivalent as A weighting sound pressure level（Ldn）. The control group was housed to the same conditions without the transformer noise.The back noise of the experimental box is less than 35 d B. The neurotransmitter and nervoustissue of the hippocampus area in SD rats were determined after a 35-day noise exposure

as well as the expression levels of Ca N and Ca MKII subunit. Neurotransmitter was determinated by high-performance liquid chromatography. Results revealed no significant difference（P>0.05） between exposed group and control group with Glu

GABA

5–HT and DA. Ultrastructure of neurons and synapses in hippocampus of SD rats were observed by transmission electron microscopy. No significant difference（P>0.05） was found in the neuronal ultrastructure and synaptic ultrastructure. Western blot was used to detect the expression levels of Ca N and Ca MKII subunit. And there was no significant difference（P>0.05） in protein expression assay（expression of Ca N A and Ca MKII α subunit）. Exposure of the 60 d B and 65 d B transformer noise in 35 days does not affect the SD rat hippocampus neuronal apoptosis and expression of Ca N and Ca MKII. The transformer noise about the substation is less than 65 d B daytime as a weighting sound pressure level

and 55 d B at night. The main frequency component is below 500 Hz. High frequency components are low and decaying fast. This steady noise is much lower than traffic and factory noise which is not enough to cause changes in neurotransmitter and hippocampal tissue structure in SD rats. In conclusion

60 d B and 65 d B of transformer noise（Ldn） have no effect on the neurotransmitter and nervoustissue in hippocampus of SD rats.