Picosecond Pulse Electrical Field Suppressing Spike Firing in Hippocampal CA1 in Rat In Vivo

Picosecond pulse electrical fields (psPEFs), due to their high temporal-resolution accuracy and localization, were viewed as a potential targeted and noninvasive method for neuromodulation. However, few studies have reported psPEFs regulating neuronal activity in vivo. In this paper, a preliminary study on psPEFs regulating action potentials in hippocampus CA1 of rats in vivo was carried out. By analyzing the neuronal spike firing rate in hippocampus CA1 pre- and post-psPEF stimulation, effects of frequency, duration, and dosimetry of psPEFs were studied. The psPEF used in this study had a pulse width of 500 ps and a field strength of 1 kV/mm, established by 1 kV picosecond voltage pulses. Results showed that the psPEF suppressed spike firing in hippocampal CA1 neurons. The suppression effect was found to be significant except for 10 s, 10 Hz. For short-duration stimulation (10 s), the inhibition rate of spike firing increased with frequency. At longer stimulation durations (1 and 2 min), the inhibition rate increased and decreased alternately as the frequency increased. Despite this, the inhibition rate at high frequencies (5 and 10 kHz) was significantly larger than that at 10 and 100 Hz. A cumulative effect of psPEF on spike firing inhibition was found at low frequencies (10 and 100 Hz), which was saturated when frequency reached 500 Hz or higher. This paper conducts a study on psPEF regulating spike firing in hippocampal CA1 in vivo for the first time and guides subsequent study on psPEF achieving noninvasive neuromodulation.