Effects of Infrasound on Changes of Intracellular Calcium Ion Concentration and on Expression of RyRs in Hippocampus of Rat Brain

In the present study, we investigated the molecular biological effect of infrasound on changes of intracellular free Ca 2+ concentration ([Ca 2+ ]i) and on expression of ryanodine receptors (RyRs) in the hippocampus of rats. 60 SD rats were randomized into ten groups and examined for [Ca 2+ ]i and RyRs expression after exposure to 8Hz 90dB infrasound at days 1, 7, 14 and 21. Groups exposed to infrasound were exposed to 8Hz 90dB infrasound for 2 hours once daily. Acute cell separation, fluo-3/AM fluorescence technique and laser scanning confocal microscope (LSCM) were used for measurement of the [Ca 2+ ]i level. There was no significant difference of [Ca 2+ ]i at 1d and 7d infrasound exposure groups compared to control, but there was a significant incease at 14d group (p<0.01) and 21d group (p<0.05). Immunohistochemistry indicated the expression of RyRs in CA1 and CA3 pyramidal cells of the hippocampus showed no difference at 1d and 7d groups compared to control, whereas significant decrease was observed at 14d group (p<0.01) and 21d group (p<0.05). The data suggest that infrasound of 8Hz 90dB can induce [Ca 2+ ]i increase and decrease the expression of RyRs in CA1 and CA3 regions of the hippocampus after exposure to infrasound for 14 and 21 days.