谷氨酸和N-甲基-D-天冬氨酸以电压依赖性方式影响小龙虾轴突终末的释放。
Glutamate and N-methyl-D-aspartate affect release from crayfish axon terminals in a voltage-dependent manner.
作者信息
Parnas H, Parnas I, Ravin R, Yudelevitch B
机构信息
Otto Loewi Center for Cellular and Molecular Neurobiology, Hebrew University of Jerusalem, Israel.
出版信息
Proc Natl Acad Sci U S A. 1994 Nov 22;91(24):11586-90. doi: 10.1073/pnas.91.24.11586.
In the crayfish neuromuscular junction, the excitatory transmitter is glutamate. The present study shows that at concentrations as low as 5 x 10(-7) M, glutamate affects the depolarization-evoked release of neurotransmitter. Furthermore, the effect of glutamate on release is voltage-dependent and depends on the level of the depolarizing pulse. Nerve terminals were exposed to 5 x 10(-7) M tetrodotoxin and then depolarized to different levels by a macropatch electrode. Depending on the amplitude of the depolarizing pulse, glutamate (5 x 10(-7) to 1 x 10(-5) M) had a dual effect on release. At small depolarizing pulses, glutamate reduced release, whereas at large depolarizing pulses, it enhanced it. Glutamate at 10(-6) M had no significant effect on action-potential-induced release. At 10(-4) M glutamate, the action-potential-induced release was always inhibited. N-Methyl-D-aspartate was found to mimic one of the effects of glutamate: N-methyl-D-aspartate (10(-7) to 10(-5) M) reduced release at small depolarizing pulses but had no effect with larger depolarizations. 2-Amino-5-phosphonovaleric acid blocked the effect of N-methyl-D-aspartate.
在小龙虾神经肌肉接头处，兴奋性递质是谷氨酸。本研究表明，谷氨酸在低至5×10⁻⁷ M的浓度下，就会影响去极化诱发的神经递质释放。此外，谷氨酸对释放的影响是电压依赖性的，并且取决于去极化脉冲的幅度。将神经末梢暴露于5×10⁻⁷ M的河豚毒素中，然后通过膜片钳电极将其去极化到不同水平。根据去极化脉冲的幅度，谷氨酸（5×10⁻⁷至1×10⁻⁵ M）对释放具有双重作用。在小幅度去极化脉冲时，谷氨酸减少释放，而在大幅度去极化脉冲时，它增强释放。10⁻⁶ M的谷氨酸对动作电位诱发的释放没有显著影响。在10⁻⁴ M谷氨酸时，动作电位诱发的释放总是受到抑制。发现N-甲基-D-天冬氨酸能模拟谷氨酸的一种作用：N-甲基-D-天冬氨酸（10⁻⁷至10⁻⁵ M）在小幅度去极化脉冲时减少释放，但在较大去极化时没有作用。2-氨基-5-磷酸戊酸阻断了N-甲基-D-天冬氨酸的作用。
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