Chiappinelli V A, Hue B, Mony L, Sattelle D B
Department of Zoology, University of Cambridge, UK.
J Exp Biol. 1989 Jan;141:61-71. doi: 10.1242/jeb.141.1.61.
A comparison was made between the effects of kappa-bungarotoxin and alpha-bungarotoxin upon nicotinic cholinergic transmission at an identified synapse (the cereal afferent, giant interneurone 2 synapse) in the central nervous system of the cockroach (Periplaneta americana). kappa-Bungarotoxin, a snake venom kappa-neurotoxin, completely blocked nicotinic unitary excitatory postsynaptic potentials (EPSPs) and evoked composite EPSPs when applied at a concentration of 1.0 x 10(-7) moll-1. No recovery was observed after a 2h wash in normal saline. kappa-Bungarotoxin produced a decrease in acetylcholine-induced nicotinic responses which paralleled decreases in nicotinic synaptic potentials and currents, indicating that kappa-bungarotoxin blocked postsynaptic nicotinic receptors. This blockade appeared to be specific as resting membrane potential, input resistance and the ability to elicit an action potential in response to direct stimulation of giant interneurone 2 were unchanged following prolonged toxin exposures. Samples of alpha-bungarotoxin which were free from kappa-neurotoxin contamination were also found to be potent antagonists of cockroach neuronal nicotinic receptors. It is concluded that the cockroach receptor is the first reported example of a neuronal nicotinic receptor which is sensitive to blockade by both kappa-neurotoxins and alpha-neurotoxins.
对κ-银环蛇毒素和α-银环蛇毒素对蟑螂（美洲大蠊）中枢神经系统中一个已确定突触（谷物传入神经、巨大中间神经元2突触）的烟碱型胆碱能传递的影响进行了比较。κ-银环蛇毒素是一种蛇毒κ-神经毒素，当以1.0×10⁻⁷mol·l⁻¹的浓度应用时，它完全阻断了烟碱型单突触兴奋性突触后电位（EPSP）并诱发复合EPSP。在生理盐水中冲洗2小时后未观察到恢复。κ-银环蛇毒素使乙酰胆碱诱导的烟碱型反应降低，这与烟碱型突触电位和电流的降低平行，表明κ-银环蛇毒素阻断了突触后烟碱型受体。这种阻断似乎具有特异性，因为在长时间暴露于毒素后，静息膜电位、输入电阻以及对直接刺激巨大中间神经元2引发动作电位的能力均未改变。还发现不含κ-神经毒素污染的α-银环蛇毒素样品也是蟑螂神经元烟碱型受体的有效拮抗剂。得出的结论是，蟑螂受体是首个被报道的对κ-神经毒素和α-神经毒素的阻断均敏感的神经元烟碱型受体实例。
