Partial suppression of GABAA-mediated inhibition induces spatially restricted epileptiform activity in guinea pig neocortical slices.
The spatio-temporal distribution of evoked activity in guinea pig neocortical slices was investigated during partial suppression of gamma-aminobutyric acid (GABA)A-mediated synaptic inhibition with different concentrations of bicuculline. Activity patterns were recorded by use of a voltage-sensitive dye and a fast optical recording technique. At non-epileptogenic concentrations of bicuculline (0.6-2.5 microM), evoked potentials were of longer duration and larger amplitude, but the spatial extent of spread in the horizontal direction was unaffected. At threshold epileptogenic concentrations of bicuculline (1.25-5 microM), spatially restricted epileptiform activity developed at a distance from the stimulation site which was clearly separated from potentials with non-epileptic characteristics close to the stimulation site. It is concluded that, under moderate disinhibition, stimulus-evoked activity has a suppressive effect on spread and development of epileptiform activity, probably through synchronous activation of still-functioning inhibitory circuits.
Langenstroth
M
M
Neurobiological Laboratories, Max-Planck-Institute for Biophysical Chemistry, Göttingen, Germany.
Albowitz
B
B
Kuhnt
U
U
D000818:Animals; D002540:Cerebral Cortex / Q000737:chemistry* / Q000503:physiopathology*; D004558:Electric Stimulation; D004827:Epilepsy / Q000503:physiopathology*; D005071:Evoked Potentials / Q000502:physiology; D005456:Fluorescent Dyes; D058787:GABA-A Receptor Antagonists; D006168:Guinea Pigs; D009433:Neural Inhibition / Q000502:physiology; D009924:Organ Culture Techniques; D013343:Styrenes
D005456:Fluorescent Dyes; D058787:GABA-A Receptor Antagonists; C096453:RH 795; D013343:Styrenes