Nishikawa K, Kidokoro Y
Institute for Behavioral Sciences, Gunma University School of Medicine, 3-39-22 Showa-machi, Maebashi 371-8511, Japan.
Brain Res. 1999 Aug 7;837(1-2):67-74. doi: 10.1016/s0006-8993(99)01676-5.
The effect of octopamine, a biogenic amine, on synaptic transmission at the neuromuscular junction (NMJ) in first instar larvae of Drosophila melanogaster was examined using the patch clamp technique. Muscle cells were voltage-clamped at -60 mV in the whole-cell configuration, and nerve-evoked excitatory junctional currents (EJCs) and miniature excitatory junctional currents (MEJCs) were recorded. Octopamine significantly decreased the mean amplitude of nerve-evoked EJCs in a dose-dependent manner and increased the failure rate. However, the mean amplitude and amplitude distribution of MEJCs were not affected by octopamine. These results suggest that octopamine is acting presynaptically. This effect was abolished by pretreatment with the octopamine receptor blocker, yohimbine. On the other hand, octopamine significantly decreased the decay time constant of MEJCs from 6.0+/-0.3 ms (mean+/-S.E., n=16) to 4.2+/-0.3 ms (n=14) (p<0.001), which might be the effect on the kinetic properties of junctional glutamate receptor channels. However, the mean open time of extrajunctional glutamate receptor channels was not changed by octopamine. Taken together, these results suggest that octopamine inhibits synaptic transmission by affecting both pre- and postsynaptic mechanisms.
利用膜片钳技术研究了生物胺章鱼胺对黑腹果蝇一龄幼虫神经肌肉接头（NMJ）突触传递的影响。在全细胞模式下，将肌肉细胞电压钳制在-60 mV，并记录神经诱发的兴奋性接头电流（EJC）和微小兴奋性接头电流（MEJC）。章鱼胺以剂量依赖性方式显著降低神经诱发EJC的平均幅度，并增加失败率。然而，MEJC的平均幅度和幅度分布不受章鱼胺影响。这些结果表明章鱼胺作用于突触前。用章鱼胺受体阻断剂育亨宾预处理可消除这种作用。另一方面，章鱼胺使MEJC的衰减时间常数从6.0±0.3 ms（平均值±标准误，n = 16）显著降低至4.2±0.3 ms（n = 1）（p<0.001），这可能是对接头谷氨酸受体通道动力学特性的影响。然而，接头外谷氨酸受体通道的平均开放时间不受章鱼胺影响。综上所述，这些结果表明章鱼胺通过影响突触前和突触后机制来抑制突触传递。
