Andersen Jonas L, MacMillan Heath A, Overgaard Johannes
Department of Zoophysiology, Faculty of Science and Technology, Aarhus University, Aarhus DK-8000, Denmark
Department of Zoophysiology, Faculty of Science and Technology, Aarhus University, Aarhus DK-8000, Denmark.
J Exp Biol. 2015 Aug;218(Pt 16):2492-5. doi: 10.1242/jeb.123760. Epub 2015 Jun 18.
Chill-susceptible insects enter a reversible paralytic state, termed chill coma, at mild low temperatures. Chill coma is caused by neuromuscular impairment, allegedly triggered by cold-induced depolarization of muscle resting membrane potential (Vm). We used five Drosophila species that vary in cold tolerance (chill coma temperature spanning ∼11°C) and repeatedly measured muscle Vm during a downward temperature ramp (20 to -3°C). Cold-tolerant species were able to defend their Vm down to lower temperatures, which is not explained by species-specific differences in initial Vm at 20°C, but by cold-tolerant drosophilids defending Vm across a broad range of temperatures. We found support for a previously suggested 'critical threshold' of Vm, related to chill coma, in three of the five species. Interestingly, the cold-tolerant Drosophila species may enter coma as a result of processes unrelated to muscle depolarization as their Vm was not significantly depolarized at their chill coma temperatures.
对寒冷敏感的昆虫在轻度低温下会进入一种可逆的麻痹状态，称为冷昏迷。冷昏迷是由神经肌肉损伤引起的，据说是由寒冷导致的肌肉静息膜电位（Vm）去极化触发的。我们使用了五种耐寒性不同（冷昏迷温度跨度约为11°C）的果蝇物种，并在温度下降斜坡（20至 -3°C）期间反复测量肌肉Vm。耐寒物种能够在更低的温度下维持其Vm，这并非由20°C时初始Vm的物种特异性差异所解释，而是由耐寒果蝇在广泛的温度范围内维持Vm所致。我们在五个物种中的三个物种中发现了对先前提出的与冷昏迷相关的Vm“临界阈值”的支持。有趣的是，耐寒果蝇物种可能由于与肌肉去极化无关的过程而进入昏迷，因为它们的Vm在其冷昏迷温度下并未显著去极化。
