Araque A, Clarac F, Buño W
Instituto Cajal Consejo Superior de Investigaciones Cientificas, Madrid, Spain.
Proc Natl Acad Sci U S A. 1994 May 10;91(10):4224-8. doi: 10.1073/pnas.91.10.4224.
The toxin fraction (FTX) and peptide omega-Aga-IVA from the venom of the funnel-web spider Agelenopsis aperta, as well as a synthetic analogue of FTX, specifically block the P-type voltage-dependent Ca2+ channel (VDCC). The effects of these toxins on synaptic transmission were studied in the neuromuscular synapses of the crayfish opener muscle, which has a single excitatory and a single inhibitory motoneuron. FTX selectively and reversibly blocked excitatory and inhibitory postsynaptic currents and potentials in a dose-dependent manner. FTX had no effect on (i) resting and postsynaptic membrane conductance, (ii) postsynaptic L-type VDCC, and (iii) both glutamate- and gamma-aminobutyric acid-induced postsynaptic responses. Mean amplitude and frequency of miniature postsynaptic potentials were unchanged by FTX. The postsynaptic VDCC was inhibited by nifedipine, a selective dihydropyridine antagonist of L-type VDCC, whereas synaptic transmission was unaffected. Transmission was also undisturbed by omega-conotoxin, suggesting that N-type VDCCs are not involved. The peptide omega-Aga-IVA blocked excitatory and inhibitory transmission without affecting postsynaptic VDCC. Synaptic transmission was also blocked by synthetic FTX. We conclude that presynaptic P-type VDCCs are involved in both evoked excitatory and inhibitory transmitter release in crayfish neuromuscular synapses.
来自漏斗网蜘蛛（Agelenopsis aperta）毒液的毒素组分（FTX）和ω-Aga-IVA肽，以及FTX的一种合成类似物，能特异性阻断P型电压依赖性Ca2+通道（VDCC）。在小龙虾展肌的神经肌肉突触中研究了这些毒素对突触传递的影响，该突触有一个兴奋性运动神经元和一个抑制性运动神经元。FTX以剂量依赖性方式选择性且可逆地阻断兴奋性和抑制性突触后电流及电位。FTX对以下方面无影响：（i）静息和突触后膜电导；（ii）突触后L型VDCC；（iii）谷氨酸和γ-氨基丁酸诱导的突触后反应。微小突触后电位的平均幅度和频率不受FTX影响。L型VDCC的选择性二氢吡啶拮抗剂硝苯地平可抑制突触后VDCC，但突触传递不受影响。ω-芋螺毒素也不干扰突触传递，这表明N型VDCC不参与其中。ω-Aga-IVA肽可阻断兴奋性和抑制性传递，但不影响突触后VDCC。合成FTX也可阻断突触传递。我们得出结论，突触前P型VDCC参与小龙虾神经肌肉突触中诱发的兴奋性和抑制性递质释放。
