Department of Psychology and Neuroscience, University of Colorado, Boulder, Colorado 80309.
Department of Comparative Medicine, Yale University School of Medicine, New Haven, Connecticut 06520, and.
J Neurosci. 2019 Jun 12;39(24):4829-4841. doi: 10.1523/JNEUROSCI.1167-18.2019. Epub 2019 Apr 10.
Absence epilepsy is a heritable human neurological disorder characterized by brief nonconvulsive seizures with behavioral arrest, moderate-to-severe loss of consciousness (absence), and distinct spike-wave discharges (SWDs) in the EEG and electrocorticogram (ECoG). Genetic models of this disorder have been created by selectively inbreeding rats for absence seizure-like events with similar electrical and behavioral characteristics. However, these events are also common in outbred laboratory rats, raising concerns about whether SWD/immobility accurately reflects absence epilepsy as opposed to "normal" rodent behavior. We hypothesized that, if SWD/immobility models absence seizures, it would not exist in wild-caught rats due to the pressures of natural selection. To test this hypothesis, we compared chronic video/electrocorticogram recordings from male and female wild-caught (Brown-Norway [BN]) rats to recordings from laboratory outbred BN, outbred Long-Evans, and inbred WAG/Rij rats (i.e., a model of absence epilepsy). Wild-caught BN rats displayed absence-like SWD/immobility events that were highly similar to outbred BN rats in terms of spike-wave morphology, frequency, diurnal rhythmicity, associated immobility, and sensitivity to the anti-absence drug, ethosuximide; however, SWD bursts were less frequent and of shorter duration in wild-caught and outbred BN rats than the outbred Long-Evans and inbred WAG/Rij strains. We conclude that SWD/immobility in rats does not represent absence seizures, although they appear to have many similarities. In wild rats, SWD/immobility appears to represent normal brain activity that does not reduce survival in natural environments, a conclusion that logically extends to outbred laboratory rats and possibly to those that have been inbred to model absence epilepsy. Spike-wave discharges (SWDs), behavioral arrest, and diminished consciousness are cardinal signs of seizures in human absence epilepsy and are used to model this disorder in inbred rats. These characteristics, however, are routinely found in outbred laboratory rats, leading to debate on whether SWD/immobility is a valid model of absence seizures. The SWD/immobility events in wild-caught rats appear equivalent to those found in outbred and inbred rat strains, except for lower incidence and shorter durations. Our results indicate that the electrophysiological and behavioral characteristics of events underlying hypothetical absence epilepsy in rodent models are found in wild rats captured in their natural environment. Other criteria beyond observation of SWDs and associated immobility are required to objectively establish absence epilepsy in rat models.
失神发作是一种遗传性人类神经紊乱,其特征为短暂的非惊厥性发作、行为中止、意识中度至重度丧失(失神)以及脑电图和皮质电图中明显的棘慢波放电(SWD)。通过选择性近亲繁殖具有类似电和行为特征的发作样事件,已经建立了这种疾病的遗传模型。然而,这些事件在杂交实验室大鼠中也很常见,这引起了人们的关注,即 SWD/不动是否准确反映失神发作,而不是“正常”啮齿动物行为。我们假设,如果 SWD/不动模型代表失神发作,由于自然选择的压力,它不会存在于野生捕获的大鼠中。为了验证这一假设,我们比较了雄性和雌性野生捕获(布朗-挪威[BN])大鼠的慢性视频/皮质电图记录与实验室杂交 BN、杂交长耳和近交 WAG/Rij 大鼠(即失神发作模型)的记录。野生捕获的 BN 大鼠表现出失神样 SWD/不动事件,其棘波形态、频率、昼夜节律性、相关不动性和对抗失神药物 ethosuximide 的敏感性与杂交 BN 大鼠非常相似;然而,SWD 爆发在野生捕获和杂交 BN 大鼠中的频率较低,持续时间较短,而在杂交长耳和近交 WAG/Rij 大鼠中则较高。我们得出的结论是,大鼠中的 SWD/不动并不代表失神发作,尽管它们似乎有许多相似之处。在野生大鼠中,SWD/不动似乎代表正常的大脑活动,不会降低在自然环境中的生存能力,这一结论在逻辑上扩展到杂交实验室大鼠,甚至可能扩展到那些为了模拟失神发作而近交的大鼠。棘慢波放电(SWD)、行为中止和意识减退是人类失神性癫痫发作的主要特征,用于近交大鼠模拟这种疾病。然而,这些特征在杂交实验室大鼠中经常被发现,这导致了关于 SWD/不动是否是失神发作的有效模型的争论。野生捕获大鼠中的 SWD/不动事件与杂交和近交大鼠中发现的事件相当,只是发生率较低,持续时间较短。我们的结果表明,在啮齿动物模型中假设的失神性癫痫发作的潜在电生理和行为特征存在于在其自然环境中捕获的野生大鼠中。除了观察到 SWD 和相关的不动之外,还需要其他客观标准来在大鼠模型中建立失神性癫痫。