Ottea J A, Payne G T, Bloomquist J R, Soderlund D M
Department of Entomology, New York State Agricultural Experiment Station, Cornell University, Geneva 14456.
Mol Pharmacol. 1989 Aug;36(2):280-4.
BTG 502 [(2E,4E)-N-(1,2-dimethyl)-propyl-6-(5-bromonaphth-2-yl)-hexa -2,4- dienamide], a synthetic analog of insecticidal amides isolated from Piper species, stimulated 22Na+ uptake into mouse brain synaptoneurosomes in the presence of saturating concentrations of Leiurus quinquestriatus venom but had no effect on sodium uptake in the absence of venom. In the presence of Leiurus venom, half-maximal stimulation was achieved at a BTG 502 concentration of 1.7 microM, whereas maximal stimulation (2.3-fold greater than nonspecific uptake) was observed at 50 microM. In the absence of other modifiers, BTG 502 inhibited batrachotoxin (BTX)-dependent sodium uptake, producing 50% inhibition at 2 microM. In the presence of Leiurus venom, BTG 502 was a partial inhibitor of BTX-dependent 22Na+ uptake, producing half-maximal inhibition at 1.5 microM. The levels of residual BTX-dependent sodium uptake and maximal BTG 502-dependent sodium uptake measured in the presence of Leiurus venom were identical. BTG 502 inhibited the specific binding of [3H]batrachotoxinin A-20-alpha-benzoate (BTX-B) to the activator recognition site (site 2) of sodium channels in these preparations, producing half-maximal inhibition at 2 microM and maximal inhibition at 30 microM. Equilibrium analysis showed that BTG 502 was an apparent competitive inhibitor of [3H]BTX-B binding, producing a concentration-dependent decrease in the affinity of sodium channels for this ligand without affecting binding capacity. Kinetic analysis demonstrated that BTG 502 slowed the rate of formation of the ligand-receptor complex but did not alter the rate of dissociation of this complex. The effects of BTG 502 on 22Na+ uptake and [3H]BTX-B binding are consistent with the action of this compound as an antagonist at the activator recognition site of the voltage-sensitive sodium channel in the absence of Leiurus venom and as a partial agonist at this site in the presence of Leiurus venom. These results suggest that the N-alkylamides represent a novel chemical class of neurotoxins that act at site 2 of the sodium channel.
BTG 502 [（2E，4E）-N-（1,2-二甲基）-丙基-6-（5-溴萘-2-基）-己-2,4-二烯酰胺]，一种从胡椒属植物中分离出的杀虫酰胺类合成类似物，在存在饱和浓度的金环蛇毒的情况下，能刺激22Na+摄入小鼠脑突触神经小体，但在没有毒液的情况下对钠摄取没有影响。在有金环蛇毒存在时，BTG 502浓度为1.7微摩尔时达到半数最大刺激，而在50微摩尔时观察到最大刺激（比非特异性摄取大2.3倍）。在没有其他调节剂的情况下，BTG 502抑制了依赖于蛙毒素（BTX）的钠摄取，在2微摩尔时产生50%的抑制。在有金环蛇毒存在时，BTG 502是依赖于BTX的22Na+摄取的部分抑制剂，在1.5微摩尔时产生半数最大抑制。在有金环蛇毒存在时测得的残余依赖于BTX的钠摄取水平和最大依赖于BTG 502的钠摄取水平是相同的。BTG 502抑制了[3H]蛙毒素A-20-α-苯甲酸酯（BTX-B）与这些制剂中钠通道激活剂识别位点（位点2）的特异性结合，在2微摩尔时产生半数最大抑制，在30微摩尔时产生最大抑制。平衡分析表明，BTG 502是[3H]BTX-B结合的明显竞争性抑制剂，使钠通道对该配体的亲和力呈浓度依赖性降低，而不影响结合能力。动力学分析表明，BTG 502减慢了配体-受体复合物的形成速率，但没有改变该复合物的解离速率。BTG 502对22Na+摄取和[3H]BTX-B结合的影响与该化合物在没有金环蛇毒时作为电压敏感性钠通道激活剂识别位点的拮抗剂以及在有金环蛇毒时作为该位点的部分激动剂的作用一致。这些结果表明，N-烷基酰胺代表了一类作用于钠通道位点2的新型神经毒素化学类别。
