Connexin36 knockout mice display increased sensitivity to pentylenetetrazol-induced seizure-like behaviors.
OBJECTIVE
Large-scale synchronous firing of neurons during seizures is modulated by electrotonic coupling between neurons via gap junctions. To explore roles for connexin36 (Cx36) gap junctions in seizures, we examined the seizure threshold of connexin36 knockout (Cx36KO) mice using a pentylenetetrazol (PTZ) model.


METHODS
Mice (2-3months old) with Cx36 wildtype (WT) or Cx36KO genotype were treated with vehicle or 10-40mg/kg of the convulsant PTZ by intraperitoneal injection. Seizure and seizure-like behaviors were scored by examination of video collected for 20min. Quantitative real-time PCR (QPCR) was performed to measure potential compensatory neuronal connexin (Cx30.2, Cx37, Cx43 and Cx45), pannexin (PANX1 and PANX2) and gamma-aminobutyric acid type A (GABA(A)) receptor α1 subunit gene expression.


RESULTS
Cx36KO animals exhibited considerably more severe seizures; 40mg/kg of PTZ caused severe generalized (≥grade III) seizures in 78% of KO, but just 5% of WT mice. A lower dose of PTZ (20mg/kg) induced grade II seizure-like behaviors in 40% KO vs. 0% of WT animals. There was no significant difference in either connexin, pannexin or GABA(A) α1 gene expression between WT and KO animals.


CONCLUSIONS
Increased sensitivity of Cx36KO animals to PTZ-induced seizure suggests that Cx36 gap junctional communication functions as a physiological anti-convulsant mechanism, and identifies the Cx36 gap junction as a potential therapeutic target in epilepsy.
Jacobson
Gregory M
GM
Department of Engineering, University of Waikato, Hamilton, New Zealand. jacobson@waikato.ac.nz
Voss
Logan J
LJ
Melin
Sofia M
SM
Mason
Jonathan P
JP
Cursons
Ray T
RT
Steyn-Ross
D Alistair
DA
Steyn-Ross
Moira L
ML
Sleigh
James W
JW
D000818:Animals; D001522:Behavior, Animal / Q000187:drug effects*; D017630:Connexins / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D003292:Convulsants; D018076:DNA, Complementary / Q000096:biosynthesis / Q000235:genetics; D005260:Female; D017629:Gap Junctions / Q000378:metabolism; D007274:Injections, Intraperitoneal; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D009419:Nerve Tissue Proteins / Q000378:metabolism; D009434:Neural Pathways / Q000502:physiology; D010433:Pentylenetetrazole; D011963:Receptors, GABA-A / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012640:Seizures / Q000139:chemically induced* / Q000523:psychology*; D013569:Synapses / Q000502:physiology; D000097004:Gap Junction delta-2 Protein
D017630:Connexins; D003292:Convulsants; D018076:DNA, Complementary; D009419:Nerve Tissue Proteins; D010433:Pentylenetetrazole; D011963:Receptors, GABA-A; D000097004:Gap Junction delta-2 Protein; C546241:Gabra1 protein, mouse; C503631:Panx1 protein, mouse; C516139:Panx2 protein, mouse