title: Effects of infrasound at 8 Hz 90 dB/130 dB on NMDAR1 expression and changes in intracellular calcium ion concentration in the hippocampus of rats.
abstract: In the present study, we investigated the effect of infrasound on the expression of N-methyl-D-aspartate (NMDAR)1 as well as changes in intracellular calcium ion concentration ([Ca2+]i) in the hippocampus of rats. Sprague-Dawley (SD) rats were exposed for 2 h daily to infrasound at 8 Hz 90 dB or 130 dB, and NMDAR1 expression was examined on days 1, 7, 14, 21 and 28. The expression of NMDAR1 in the rat hippocampus upon exposure to infrasound at 8 Hz 90 dB sound pressure level (SPL) showed an initial decrease on day 1, an increase on days 7 and 14, a further decrease on day 21, and a return to normal levels on day 28. The peak level was observed on day 14 in every examined subregion of the hippocampus. By contrast, exposure to infrasound at 8 Hz 130 dB SPL had opposite effects, showing an increase on day 1, a decrease on day 7, a decrease to the lowest point on days 14, another increase on day 21 and a return to normal levels on day 28. The lowest expression of NMDAR1 was found in the CA1 and CA3 regions on day 14 and in the DG region on day 7 with exposure at 130 dB. There were significant differences in [Ca2+]i concentration on days 14 and 21 with infrasonic exposure at both 8 Hz 90 dB and 130 dB, but no significant differences in [Ca2+]i concentration on days 1, 7 and 28 compared to the control group. The highest [Ca2+]i level was noted on day 14 with infrasound exposure at 8 Hz 130 dB. These changes suggest that 8 Hz 90 dB/130 dB infrasound exposure induced certain reversible changes in NMDAR1 expression and [Ca2+]i concentration in hippocampal cells, which may influence mnemonic functions related to the hippocampus.
authors.affiliation: Department of Physiotherapy and Rehabilitation, Tangdu Hospital, Fourth Military Medical University, Xi'an 710038, P.R. China.
authors.forename: Zhao-Hui
authors.initials: ZH
authors.lastname: Liu
authors.forename: Jing-Zao
authors.initials: JZ
authors.lastname: Chen
authors.forename: Lin
authors.initials: L
authors.lastname: Ye
authors.forename: Jing
authors.initials: J
authors.lastname: Liu
authors.forename: Jian-Yong
authors.initials: JY
authors.lastname: Qiu
authors.forename: Jian
authors.initials: J
authors.lastname: Xu
authors.forename: Rui
authors.initials: R
authors.lastname: Lu
authors.forename: Xiao-Chao
authors.initials: XC
authors.lastname: Yuan
authors.forename: Wen-Dong
authors.initials: WD
authors.lastname: Zhang
authors.forename: Xiao-Fang
authors.initials: XF
authors.lastname: Li
authors.forename: Gong
authors.initials: G
authors.lastname: Li