Zhu Yuechen, de Castro Leo, Cooper Robin Lewis
Department of Biology, University of Kentucky, Lexington, KY 40506-0225, USA.
Massachusetts Institute of Technology, Electrical Engineering and Computer Science (EECS), 50 Vassar St, Cambridge, MA 02142, USA.
Biol Open. 2018 Dec 12;7(12):bio037820. doi: 10.1242/bio.037820.
Ectothermic animals in areas characterised by seasonal changes are susceptible to extreme fluctuations in temperature. To survive through varied temperatures, ectotherms have developed unique strategies. This study focuses on synaptic transmission function at cold temperatures, as it is a vital component of ectothermic animals' survival. For determining how synaptic transmission is influenced by an acute change in temperature (20°C to 10°C within a minute) and chronic cold (10°C), the crayfish () neuromuscular junction (NMJ) was used as a model. To simulate chronic cold conditions, crayfish were acclimated to 15°C for 1 week and then to 10°C for 1 week. They were then used to examine the synaptic properties associated with the low output nerve terminals on the opener muscle in the walking legs and high output innervation on the abdominal deep extensor muscle. The excitatory postsynaptic potentials (EPSPs) of the opener NMJs increased in amplitude with acute warming (20°C) after being acclimated to cold; however, the deep extensor muscles showed varied changes in EPSP amplitude. Synaptic transmission at both NMJs was enhanced with exposure to the modulators serotonin or octopamine. The membrane resistance of the muscles decreased 33% and the resting membrane potential hyperpolarised upon warm exposure. Analysis of haemolymph indicated that octopamine increases during cold exposure. These results suggest bioamine modulation as a possible mechanism for ensuring that synaptic transmission remains functional at low temperatures.
在以季节变化为特征的地区，变温动物易受温度极端波动的影响。为了在不同温度下生存，变温动物已发展出独特的策略。本研究聚焦于低温下的突触传递功能，因为它是变温动物生存的重要组成部分。为了确定突触传递如何受到温度急性变化（一分钟内从20°C降至10°C）和长期低温（10°C）的影响，以小龙虾的神经肌肉接头（NMJ）作为模型。为了模拟长期低温条件，将小龙虾先在15°C下适应1周，然后在10°C下适应1周。然后用它们来检查与步行腿中开肌上低输出神经末梢以及腹部深层伸肌上高输出神经支配相关的突触特性。适应寒冷后，开肌NMJ的兴奋性突触后电位（EPSP）幅度在急性升温（20°C）时增大；然而，深层伸肌的EPSP幅度表现出不同变化。暴露于调节剂血清素或章鱼胺时，两个NMJ的突触传递均增强。肌肉的膜电阻在温暖暴露时降低了33%，静息膜电位超极化。血淋巴分析表明，章鱼胺在寒冷暴露期间增加。这些结果表明生物胺调节可能是确保突触传递在低温下仍保持功能的一种机制。
