目的：研究四乙铵（ＴＥＡ）、４氨基吡啶（４ＡＰ）对５ＨＴ３受体介导的豚鼠回肠收缩的影响．方法：等长换能器记录回肠收缩；［３Ｈ］ＧＲ６５６３０结合试验测定５ＨＴ３受体结合特性．结果：ＴＥＡ、４ＡＰ引起回肠收缩并增强自发活动，被阿托品或ＭＤＬ７２２２２阻断．ＴＥＡ、４ＡＰ增强２甲基５ＨＴ和５ＨＴ引起的收缩；逆转托烷司琼或Ｂｅｎｅｓｅｔｒｏｎ的抑制作用；不影响卡巴胆碱引起的收缩．ＴＥＡ、４ＡＰ不影响５ＨＴ３受体结合配体．结论：ＴＥＡ、４ＡＰ可能通过阻断突触前神经元钾通道增强５ＨＴ３受体介导的回肠收缩 Objective: To study the effect of tetraethylammonium (TEA) and 4aminopyridine (4AP) on 5HT3 receptormediated ileal contraction in guinea pigs. Methods: Isometric transducers recorded ileal contraction; [3H] GR65630 binding assay to determine 5-HT3 receptor binding properties. Results: TEA, 4AP induced ileal contraction and increased spontaneous activity, which was blocked by atropine or MDL72222. TEA, 4  AP enhanced 2  methyl  5  HT and 5  HT induced contraction; reversal of tropisetron or Benesetron inhibition; does not affect carbachol - induced contraction. TEA, 4  AP does not affect 5  HT3 receptor binding ligand. CONCLUSION: TEA and 4AP may enhance i-HT3 receptor-mediated ileal contraction by blocking the presynaptic neuronal potassium channels