Biological responses to terahertz radiation with different power density in primary hippocampal neurons

Background Terahertz (THz) radiation is a valuable imaging and sensing tool which is widely used in industry and medicine. However, it biological effects including genotoxicity and cytotoxicity are not clear, particularly on the nervous system. In this study, we investigated how THz radiation with different frequency and intensity would affect the morphology, cell growth and function of rat hippocampal neurons in vitro . Methods Primary hippocampal neuronal cells were isolated from newborn Wistar rat pups and were exposed to THz radiation with the frequencies of 0.12 THz and 0.141 THz, at an power intensities of 10 mW/cm 2 and 30 mW/cm 2 respectively. The cellular activities were evaluated by Cell Counting Kit-8 after exposure for 10 min and 30 min. The cellular apoptosis was examined by Annexin V staining using flow cytometry and the ultrastructure was detected by electron microscopy. Moreover, the amount of amino acid in the cultured neurons was measured by high performance liquid chromatography (HPLC). Results No obvious morphological changes, such as axon length and axon number, could be detected in primary neurons after exposure to 10mW/cm 2 or 50 mW/cm 2 THz for 30 min. However, the overall cellular activities were differentially affected by 10mW/cm 2 and 50 mW/cm 2 THz. Obvious cellular apoptosis was induced by both 10mW/cm 2 and 50 mW/cm 2 exposure. We also found that the amounts of most amino acids did not change significantly after exposure to these two types of THz radiation. Conclusions The effects of THz radiation on hippocampal neurons depend on frequency, power, exposure time as well as the measurement time after the exposure. These results will provide important information for further investigation of the effect of THz radiation on the nervous system.