A nonsynaptic mechanism underlying interictal discharges in human epileptic neocortex.
Very fast oscillations (VFOs, >80 Hz) are important for physiological brain processes and, in excess, with certain epilepsies. Putative mechanisms for VFO include interneuron spiking and network activity in coupled pyramidal cell axons. It is not known whether either, or both, of these apply in pathophysiological conditions. Spontaneously occurring interictal discharges occur in human tissue in vitro, resected from neocortical epileptic foci. VFO associated with these discharges was manifest in both field potential and, with phase delay, in excitatory synaptic inputs to fast spiking interneurons. Recruitment of somatic pyramidal cell and interneuron spiking was low, with no correlation between VFO power and synaptic inputs to principal cells. Reducing synaptic inhibition failed to affect VFO occurrence, but they were abolished by reduced gap junction conductance. These data suggest a lack of a causal role for interneurons, and favor a nonsynaptic pyramidal cell network origin for VFO in epileptic human neocortex.
Roopun
Anita K
AK
Institute of Neuroscience, The Medical School, Framlington Place, Newcastle University, Newcastle-upon-Tyne NE2 4HH, UK.
Simonotto
Jennifer D
JD
Pierce
Michelle L
ML
Jenkins
Alistair
A
Nicholson
Claire
C
Schofield
Ian S
IS
Whittaker
Roger G
RG
Kaiser
Marcus
M
Whittington
Miles A
MA
Traub
Roger D
RD
Cunningham
Mark O
MO
D000200:Action Potentials / Q000502:physiology*; D000293:Adolescent; D000328:Adult; D002648:Child; D004569:Electroencephalography; D004594:Electrophysiology; D004827:Epilepsy / Q000503:physiopathology*; D018756:GABA Antagonists / Q000494:pharmacology; D006801:Humans; D007395:Interneurons / Q000166:cytology / Q000502:physiology; D008875:Middle Aged; D019579:Neocortex / Q000166:cytology / Q000187:drug effects / Q000502:physiology / Q000503:physiopathology*; D011724:Pyridazines / Q000494:pharmacology; D009435:Synaptic Transmission / Q000502:physiology; D013702:Temporal Lobe / Q000166:cytology / Q000187:drug effects / Q000502:physiology / Q000503:physiopathology; D055815:Young Adult
D018756:GABA Antagonists; D011724:Pyridazines; C049853:gabazine