Transient cerebral ischemia increases CA1 pyramidal neuron excitability.
In human and experimental animals, the hippocampal CA1 region is one of the most vulnerable areas of the brain to ischemia. Pyramidal neurons in this region die 2-3 days after transient cerebral ischemia whereas other neurons in the same region remain intact. The mechanisms underlying the selective and delayed neuronal death are unclear. We tested the hypothesis that there is an increase in post-synaptic intrinsic excitability of CA1 pyramidal neurons after ischemia that exacerbates glutamatergic excitotoxicity. We performed whole-cell patch-clamp recordings in brain slices obtained 24 h after in vivo transient cerebral ischemia. We found that the input resistance and membrane time constant of the CA1 pyramidal neurons were significantly increased after ischemia, indicating an increase in neuronal excitability. This increase was associated with a decrease in voltage sag, suggesting a reduction of the hyperpolarization-activated non-selective cationic current (I(h)). Moreover, after blocking I(h) with ZD7288, the input resistance of the control neurons increased to that of the post-ischemia neurons, suggesting that a decrease in I(h) contributes to increased excitability after ischemia. Finally, when lamotrigine, an enhancer of dendritic I(h), was applied immediately after ischemia, there was a significant attenuation of CA1 cell loss. These data suggest that an increase in CA1 pyramidal neuron excitability after ischemia may exacerbate cell loss. Moreover, this dendritic channelopathy may be amenable to treatment.
Department of Neurology, Baylor College of Medicine, 6501 Fannin Street, NB204, Houston, TX 77030, USA. yf139876@gmail.com
Yuan
Y
Fan
Ping
P
Deng
Yu-Chi
YC
Wang
Hui-Chen
HC
Lu
Zao C
ZC
Xu
Paul E
PE
Schulz
D000818:Animals; D002317:Cardiovascular Agents / Q000494:pharmacology; D016923:Cell Death / Q000187:drug effects / Q000502:physiology / Q000528:radiation effects; D004195:Disease Models, Animal; D004307:Dose-Response Relationship, Radiation; D004558:Electric Stimulation / Q000379:methods; D018691:Excitatory Amino Acid Antagonists / Q000494:pharmacology; D006624:Hippocampus / Q000473:pathology*; D066298:In Vitro Techniques; D002546:Ischemic Attack, Transient / Q000473:pathology*; D000077213:Lamotrigine; D008297:Male; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology* / Q000528:radiation effects; D018408:Patch-Clamp Techniques / Q000379:methods; D017966:Pyramidal Cells / Q000187:drug effects / Q000503:physiopathology* / Q000528:radiation effects; D011743:Pyrimidines / Q000494:pharmacology; D051381:Rats; D018709:Statistics, Nonparametric; D014227:Triazines / Q000494:pharmacology
D002317:Cardiovascular Agents; D018691:Excitatory Amino Acid Antagonists; D011743:Pyrimidines; D014227:Triazines; C082246:ICI D2788; D000077213:Lamotrigine