Differences in cortical versus subcortical GABAergic signaling: a candidate mechanism of electroclinical uncoupling of neonatal seizures.
Electroclinical uncoupling of neonatal seizures refers to electrographic seizure activity that is not clinically manifest. Uncoupling increases after treatment with Phenobarbital, which enhances the GABA(A) receptor (GABA(A)R) conductance. The effects of GABA(A)R activation depend on the intracellular Cl(-) concentration ([Cl(-)](i)) that is determined by the inward Cl(-) transporter NKCC1 and the outward Cl(-) transporter KCC2. Differential maturation of Cl(-) transport observed in cortical versus subcortical regions should alter the efficacy of GABA-mediated inhibition. In perinatal rat pups, most thalamic neurons maintained low [Cl(-)](i) and were inhibited by GABA. Phenobarbital suppressed thalamic seizure activity. Most neocortical neurons maintained higher [Cl(-)](i), and were excited by GABA(A)R activation. Phenobarbital had insignificant anticonvulsant responses in the neocortex until NKCC1 was blocked. Regional differences in the ontogeny of Cl(-) transport may thus explain why seizure activity in the cortex is not suppressed by anticonvulsants that block the transmission of seizure activity through subcortical networks.
Glykys
Joseph
J
Department of Neurology, Massachusetts General Hospital, Harvard Medical School, Boston, MA 02144, USA.
Dzhala
Volodymyr I
VI
Kuchibhotla
Kishore V
KV
Feng
Guoping
G
Kuner
Thomas
T
Augustine
George
G
Bacskai
Brian J
BJ
Staley
Kevin J
KJ
D000679:Amygdala / Q000254:growth & development / Q000503:physiopathology*; D000818:Animals; D000831:Animals, Newborn; D000927:Anticonvulsants / Q000494:pharmacology; D002034:Bumetanide / Q000494:pharmacology; D002712:Chlorides / Q000378:metabolism; D005260:Female; D066298:In Vitro Techniques; D008297:Male; D019579:Neocortex / Q000187:drug effects / Q000254:growth & development / Q000503:physiopathology*; D009474:Neurons / Q000502:physiology*; D010634:Phenobarbital / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D011963:Receptors, GABA-A / Q000378:metabolism; D012640:Seizures / Q000188:drug therapy / Q000503:physiopathology*; D012727:Sex Characteristics; D049994:Sodium Potassium Chloride Symporter Inhibitors / Q000494:pharmacology; D064506:Solute Carrier Family 12, Member 2; D009435:Synaptic Transmission; D013788:Thalamus / Q000187:drug effects / Q000254:growth & development / Q000503:physiopathology*; D005680:gamma-Aminobutyric Acid / Q000378:metabolism*
D000927:Anticonvulsants; D002712:Chlorides; D011963:Receptors, GABA-A; C578879:Slc12a2 protein, rat; D049994:Sodium Potassium Chloride Symporter Inhibitors; D064506:Solute Carrier Family 12, Member 2; D002034:Bumetanide; D005680:gamma-Aminobutyric Acid; D010634:Phenobarbital