Axonal and somatic filtering of antidromically evoked cortical excitation by simulated deep brain stimulation in rat brain.
Antidromic cortical excitation has been implicated as a contributing mechanism for high-frequency deep brain stimulation (DBS). Here, we examined the reliability of antidromic responses of type 2 corticofugal fibres in rat over a stimulation frequency range compatible to the DBS used in humans. We activated antidromically individual layer V neurones by stimulating their two subcortical axonal branches. We found that antidromic cortical excitation is not as reliable as generally assumed. Whereas the fast conducting branches of a type 2 axon in the highly myelinated brainstem region follow high-frequency stimulation, the slower conducting fibres in the poorly myelinated thalamic region function as low-pass filters. These fibres fail to transmit consecutive antidromic spikes at the beginning of high-frequency stimulation, but are able to maintain a steady low-frequency (6-12 Hz) spike output during the stimulation. In addition, antidromic responses evoked from both branches are rarely present in cortical neurones with a more hyperpolarized membrane potential. Our data indicate that axon-mediated antidromic excitation in the cortex is strongly influenced by the myelo-architecture of the stimulation site and the excitability of individual cortical neurones.
Chomiak
T
T
Division of Experimental Neurosciences, Department of Clinical Neurosciences, Hotchkiss Brain Institute, University of Calgary, Calgary, Alberta, Canada.
Hu
B
B
D000200:Action Potentials / Q000502:physiology; D000818:Animals; D001369:Axons / Q000502:physiology*; D001933:Brain Stem / Q000166:cytology / Q000502:physiology; D002540:Cerebral Cortex / Q000502:physiology*; D046690:Deep Brain Stimulation / Q000379:methods*; D005071:Evoked Potentials / Q000502:physiology*; D007395:Interneurons / Q000502:physiology; D008564:Membrane Potentials / Q000502:physiology; D009431:Neural Conduction / Q000502:physiology; D051381:Rats; D020318:Rats, Long-Evans; D017207:Rats, Sprague-Dawley; D013788:Thalamus / Q000166:cytology / Q000502:physiology