Lack of alpha 1b-adrenergic receptor protects against epileptic seizures.

PURPOSE:The role of alpha 1b-adrenergic receptor (alpha 1b-AR) in relation with neuronal degeneration, drug addiction, and seizure susceptibility has recently emerged. In particular, mice that overexpress alpha 1b-AR undergo spontaneous epileptic seizures and progressive neuronal loss in a variety of brain areas. Therefore, one should expect that the blockade of alpha 1b-AR leads to anticonvulsant and neuroprotective effects. However, the lack of alpha 1b-AR antagonists does not allow testing of this hypothesis. METHODS:The development of alpha 1b-AR knockout (KO) mice led us to measure seizure susceptibility and neurodegeneration following systemic excitotoxins in these mice. RESULTS:We found that alpha 1b-AR KO mice are markedly resistant to kainate- and pilocarpine-induced seizures. Moreover, when marked seizure duration and severity are obtained by doubling the dose of chemoconvulsants in alpha 1b-AR KO, neuronal degeneration never occurs. CONCLUSIONS:These data indicate that alpha 1b-AR per se plays a fundamental role in the mechanisms responsible for seizure onset, severity, and duration, whereas the brain damage observed in alpha 1b-AR-overexpressing mice is likely to be a secondary phenomenon. In fact, the absence of alpha 1b-AR confers resistance to neurotoxicity induced by seizures/chemoconvulsants. These data, although confirming a pivotal role of alpha 1b-AR in modulating seizure threshold and neuronal death, offer a novel target, which may be used to develop novel anticonvulsants and neuroprotective agents.

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