Changes in intracellular calcium concentration level accompany age‐related inhibitions of long‐term potentiation in hippocampus induced by extremely low frequency electromagnetic fields

Abstract

AbstractExtremely low frequency electromagnetic fields (ELF‐EMFs) have received increasing attention and in‐depth research due to their ability to affect learning and memory functions. However, its regulation and intrinsic mechanism at different ages in early developmental stages remains unclear. In this article, the regulation of 15 Hz/2 mT ELF‐EMFs on long‐term potentiation (LTP) persistence in the hippocampal CA1 region of Sprague–Dawley (SD) rats at early developmental stages (8‐, 15‐, 22‐, and 29‐day‐old) are investigated by electrophysiological techniques. The results show that ELF‐EMFs differentially inhibit LTP persistence due to age difference, and the younger the age, the more significant the inhibitory effect. Second, the inhibitory effect of ELF‐EMFs on LTP persistence disappeared after the addition of 2‐aminoethoxydiphenyl borate (2‐APB) to block inositol‐1,4,5‐trisphosphate receptors (IP3Rs) localized to intracellular calcium stores to reduce the intracellular calcium concentration ([Ca2+]i), proving that the LTP persistence regulated by ELF‐EMFs is associated with the IP3Rs‐mediated intracellular calcium stores. Finally, the level of [Ca2+]i was intervened by adjusting the extracellular calcium concentration([Ca2+]e). Interestingly, the inhibitory effect of ELF‐EMFs on LTP persistence in the 15‐day‐old group disappeared by increasing [Ca2+]e, whereas the inhibitory effect of ELF‐EMFs on LTP persistence in the 29‐day‐old group appeared by decreasing [Ca2+]e. Our findings reveal the underlying mechanism of the effect of ELF‐EMFs on synaptic plasticity in hippocampal CA1 area at early developmental stages and provide new insights into more rational application and protection of ELF‐EMFs.