Costello W J, Salkoff L B
J Neurosci. 1986 Dec;6(12):3634-9. doi: 10.1523/JNEUROSCI.06-12-03634.1986.
The single-gene mutant shibire (shits) is temperature-sensitive. It causes reversible paralysis at heat pulses greater than 29 degrees C by blocking synaptic transmission. The synapses of these heat-pulsed flies are depleted in vesicles but contain numerous cisternae. We report that such alterations in synaptic physiology and morphology of heat-pulsed flies can be suppressed by internal perfusion of salines with high concentrations (10-18 mM) of the divalent cations Ca2+ or Mg2+. Synaptic morphology in these perfused flies remains normal even when exposed to nonpermissive temperatures (greater than 29 degrees C); in addition, synaptic transmission maintains a high resistance to failure both in frequency and stimulus duration. We also observed many cisternae in close association with extrajunctional as well as with postsynaptic regions of the sarcolemma in heat-pulsed shits flies not perfused with the increased concentrations of divalent cations. Flies perfused with increased amounts of divalent cations lacked such cisternae in the sarcolemma. The evidence suggests that the divalent cations can mitigate an overall membrane defect expressed by the shits gene, perhaps by influencing lipid-phase transition behavior.
单基因变异体失活（shits）对温度敏感。在高于29摄氏度的热脉冲作用下，它会通过阻断突触传递导致可逆性麻痹。这些经热脉冲处理的果蝇的突触中囊泡减少，但含有大量的扁平囊。我们报告称，通过向盐溶液中内部灌注高浓度（10 - 18 mM）的二价阳离子Ca2+或Mg2+，可以抑制热脉冲果蝇突触生理学和形态学上的此类改变。即使暴露于非允许温度（高于29摄氏度）下，这些经灌注处理的果蝇的突触形态仍保持正常；此外，突触传递在频率和刺激持续时间方面都对失败保持高抗性。我们还观察到，在未灌注增加浓度二价阳离子的热脉冲失活果蝇中，许多扁平囊与肌膜的结外区域以及突触后区域紧密相连。灌注了增加量二价阳离子的果蝇的肌膜中没有此类扁平囊。证据表明，二价阳离子可能通过影响脂质相转变行为来减轻失活基因所表达的整体膜缺陷。
