High Frequency Stimulation Suppresses Compound Action Potentials In Vitro

Deep brain stimulation (DBS), also known as high frequency stimulation (HFS), is a promising method for the therapeutic control of epilepsy; although, the way DBS affects neural elements close to the stimulating electrode remains an important question. Sinusoidal HFS (50 Hz) suppresses synaptic and non-synaptic cellular neural activity in several in vitro epilepsy models. Although, the effects of HFS on axonal conduction are not known. In the present study, we tested the hypothesis that HFS suppresses local axonal conduction in vitro. HFS was locally applied to either the CA1 pyramidale cell layer or the alvear axon field of rat hippocampal slices. Complete suppression was indicated by a 100% reduction in amplitude of the field potential for the duration of the HFS. The results show that sinusoidal HFS suppresses the alvear compound action potential (CAP) as well as the CA1 antidromic evoked potential (AEP). Suppression was dependent on HFS amplitude, while HFS frequency was found not to be statistically significant. HFS applied to the alveus was more effective in suppressing the CAP than HFS applied to the CA1 pyramidale cell layer. These data suggest that HFS can block not only cellular neural firing but also activity in the axons of these cells or axons of passage