Effects of combined traffic noise on the synaptic ultrastructure and expressions of p-CaMKII and NMDAR1 in the hippocampus of young SD rats

In order to explore the effects of combined traffic noise (CTN) on learning and memory function, young Sprague-Dawley (SD) rats were exposed to CTN from highway and high-speed railway for 52 days, whose day-night equivalent continuous A-weighted sound pressure level ( L dn ) was 70 dB(A) (corresponding sound pressure level was 80 dB). The synaptic ultrastructure and the expressions of phosphorylated calcium/calmodulin-dependent protein kinase II (p-CaMKII) and N-methyl-D-aspartate receptor 1 (NMDAR1 or NR1) in the hippocampus were tested by transmission electron microscopy (TEM) and Western blot, respectively. Results showed that there was no significant difference in the synaptic ultrastructure and the expressions of p-CaMKII and NR1 in the hippocampus of young rats between the experimental group and control group. Compared with single high-speed railway noise (HSRN) with L dn of 70 dB(A), CTN had less influences on learning and memory function, which was closely related to smaller intermittency of CTN and less anxiety caused by CTN. In comparison with white noise with a sound pressure level of 80 dB, CTN had less impacts on learning and memory function, which was mainly associated with CTN’s smaller R-weighted sound pressure level based on rats’ auditory sensitivity.