Removal of superficial inhibition releases hyperexcitability in middle and deep horizontal slices from rat somatosensory neocortex.
Synaptic physiology was studied in horizontal slices of rat somatosensory neocortex. Intrinsic properties of pyramidal neurons from horizontal slices resembled those recorded in cells from coronal slices, but cells in superficial horizontal slices displayed more prominent fast and slow inhibition, while cells from deeper slices showed disinhibition. This disinhibition in deeper horizontal slices resulted in epileptogenesis in 81% of middle and 35% of deep layer horizontal slices. Brief exposure to glutamate antagonists and dantrolene was ineffective in preventing epileptic activity, but limited pentobarbital exposure reduced the proportion of deep slices manifesting epileptiform activity by 75%. Thus, within cortex inhibition dominates superficially and excitation predominates in deeper layers. While the cortex is vulnerable to hyperexcitability when superficial cortex is compromised, enhancing fast inhibition can reset the excitation-inhibition balance, and prevent epileptogenesis.
Yang
L
L
Department of Physiology and Pharmacology, State University of New York-Health Science Centre, Brooklyn 11203, USA.
Benardo
L S
LS
D018750:6-Cyano-7-nitroquinoxaline-2,3-dione / Q000494:pharmacology; D000818:Animals; D003620:Dantrolene / Q000494:pharmacology; D004558:Electric Stimulation; D018691:Excitatory Amino Acid Antagonists / Q000494:pharmacology; D019706:Excitatory Postsynaptic Potentials / Q000187:drug effects; D018757:GABA Modulators / Q000494:pharmacology; D066298:In Vitro Techniques; D009125:Muscle Relaxants, Central / Q000494:pharmacology; D019579:Neocortex / Q000187:drug effects / Q000502:physiology*; D009433:Neural Inhibition / Q000187:drug effects / Q000502:physiology*; D010424:Pentobarbital / Q000494:pharmacology; D010879:Piperazines / Q000494:pharmacology; D017966:Pyramidal Cells / Q000187:drug effects / Q000502:physiology; D051381:Rats; D012640:Seizures / Q000503:physiopathology; D013003:Somatosensory Cortex / Q000187:drug effects / Q000502:physiology*; D013569:Synapses / Q000187:drug effects / Q000502:physiology
D018691:Excitatory Amino Acid Antagonists; D018757:GABA Modulators; D009125:Muscle Relaxants, Central; D010879:Piperazines; C104291:3-(2-carboxypiperazine-4-yl)propyl-1-phosphate; D018750:6-Cyano-7-nitroquinoxaline-2,3-dione; D003620:Dantrolene; D010424:Pentobarbital