Effects on Somata by High-frequency Electrical Stimulation at The Axons of Hippocampal Pyramidal Neurons

Objective Deep brain stimulation (DBS) utilizes sustained high-frequency stimulation (HFS) of electrical pulses to modulate neuronal activity. The therapy is expected to be used to treat more brain disorders. To deeply understand the mechanisms of the HFS to advance the DBS development, the present study investigates the effect of axonal HFS on neuronal somata during HFS-induced axonal block. Methods Antidromic high-frequency stimulation (A-HFS) with a 100-Hz pulse frequency and a 1-min duration was applied at the axons of pyramidal neurons in the hippocampal CA1 region of anesthetized rats. To investigate the responses of somata, a multi-channel microelectrode array with a vertical linear configuration was implanted to record the evoked potentials in the lamellas around the somata of CA1 pyramidal neurons at the upstream area of stimulation site, including the antidromic population spikes (APS) evoked by the pulses of A-HFS as well as the orthodromic population spikes (OPS) evoked by orthodromic test pulses applied during the A-HFS. Current-source densities (CSD) of the evoked potentials were calculated to evaluate the generation and propagation of action potentials around the somata of pyramidal neurons during A-HFS. Results A-HFS on the axons of pyramidal neurons slowed down the propagation speed of both antidromic and orthodromic excitations around somata. In addition, the occurrence and recovery of the changes of somata were slower than the A-HFS-induced axonal block. Conclusion Axonal HFS can induce soma alterations that might be caused by changes in membrane potentials nearby somata. The finding is helpful for deeply revealing the mechanisms of electrical stimulations of brain nervous system.