TY - JOUR
T1 - GABAA-current rundown of temporal lobe epilepsy is associated with repetitive activation of GABAA "phasic" receptors
AU - Palma, Eleonora
AU - Roseti, Cristina
AU - Maiolino, Francesca
AU - Fucile, Sergio
AU - Martinello, Katiuscia
AU - Mazzuferi, Manuela
AU - Aronica, Eleonora
AU - Manfredi, Mario
AU - Esposito, Vincenzo
AU - Cantore, Gianpaolo
AU - Miledi, Ricardo
AU - Simonato, Michele
AU - Eusebi, Fabrizio
PY - 2007/12/26
Y1 - 2007/12/26
N2 - A study was made of the "rundown" of GABAA receptors, microtransplanted to Xenopus oocytes from surgically resected brain tissues of patients afflicted with drug-resistant human mesial temporal lobe epilepsy (mTLE). Cell membranes, isolated from mTLE neocortex specimens, were injected into frog oocytes that rapidly incorporated functional GABAA receptors. Upon repetitive activation with GABA (1 mM), "epileptic" GABAA receptors exhibited a GABAA-current (I GABA) rundown that was significantly enhanced by Zn2+ (≤250 μM), and practically abolished by the high-affinity GABAA receptor inverse agonist SR95531 (gabazine; 2.5-25 μM). Conversely, I GABA generated by "control" GABAA receptors microtransplanted from nonepileptic temporal lobe, lesional TLE, or authoptic disease-free tissues remained stable during repetitive stimulation, even in oocytes treated with Zn2+. We conclude that rundown of mTLE epileptic receptors depends on the presence of "phasic GABAA receptors" that have low sensitivity to antagonism by Zn2+. Additionally, we found that GABAA receptors, microtransplanted from the cerebral cortex of adult rats exhibiting recurrent seizures, caused by pilocarpine-induced status epilepticus, showed greater rundown than control tissue, an event also occurring in patch-clamped rat pyramidal neurons. Rundown of epileptic rat receptors resembled that of human mTLE receptors, being enhanced by Zn2+ (40 μM) and sensitive to the antiepileptic agent levetiracetam, the neurotrophin brain-derived neurotrophic factor, and the phosphatase blocker okadaic acid. Our findings point to the rundown of GABA A receptors as a hallmark of TLE and suggest that modulating tonic and phasic mTLE GABAA receptor activity may represent a useful therapeutic approach to the disease.
AB - A study was made of the "rundown" of GABAA receptors, microtransplanted to Xenopus oocytes from surgically resected brain tissues of patients afflicted with drug-resistant human mesial temporal lobe epilepsy (mTLE). Cell membranes, isolated from mTLE neocortex specimens, were injected into frog oocytes that rapidly incorporated functional GABAA receptors. Upon repetitive activation with GABA (1 mM), "epileptic" GABAA receptors exhibited a GABAA-current (I GABA) rundown that was significantly enhanced by Zn2+ (≤250 μM), and practically abolished by the high-affinity GABAA receptor inverse agonist SR95531 (gabazine; 2.5-25 μM). Conversely, I GABA generated by "control" GABAA receptors microtransplanted from nonepileptic temporal lobe, lesional TLE, or authoptic disease-free tissues remained stable during repetitive stimulation, even in oocytes treated with Zn2+. We conclude that rundown of mTLE epileptic receptors depends on the presence of "phasic GABAA receptors" that have low sensitivity to antagonism by Zn2+. Additionally, we found that GABAA receptors, microtransplanted from the cerebral cortex of adult rats exhibiting recurrent seizures, caused by pilocarpine-induced status epilepticus, showed greater rundown than control tissue, an event also occurring in patch-clamped rat pyramidal neurons. Rundown of epileptic rat receptors resembled that of human mTLE receptors, being enhanced by Zn2+ (40 μM) and sensitive to the antiepileptic agent levetiracetam, the neurotrophin brain-derived neurotrophic factor, and the phosphatase blocker okadaic acid. Our findings point to the rundown of GABA A receptors as a hallmark of TLE and suggest that modulating tonic and phasic mTLE GABAA receptor activity may represent a useful therapeutic approach to the disease.
KW - Epileptic rat
KW - Tonic
KW - Xenopus oocytes
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U2 - 10.1073/pnas.0710522105
DO - 10.1073/pnas.0710522105
M3 - Article
C2 - 18083839
AN - SCOPUS:38049120891
VL - 104
SP - 20944
EP - 20948
JO - Proceedings of the National Academy of Sciences of the United States of America
JF - Proceedings of the National Academy of Sciences of the United States of America
SN - 0027-8424
IS - 52
ER -