title: Modulation of inward rectifier potassium channel by toosendanin, a presynaptic blocker.
abstract: The effect of toosendanin, a presynaptic blocker, on the inward rectifier potassium channel (K(Kir)) of hippocampal CA1 pyramidal neurons of rats was studied by the single-channel patch-clamp technique. The results showed that toosendanin had an inhibitory effect on K(Kir) in an excised inside-out patch of the neuron under a symmetrical 150 mM K(+) condition. By decreasing the slower open time constant and increasing the slower close time constant, toosendanin (1x10(-6)-1x10(-4) g/ml) significantly reduced the open probability of the channel in a concentration-dependent manner. Meanwhile, a dose-dependent reduction in unitary conductance of the channel was also detected after toosendanin application. These data offer an explanation for toosendanin-induced facilitation of neurotransmitter release and antibotulismic effect of the drug.
authors.affiliation: Key Laboratory of Neurobiology, Institute of Physiology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, 320 Yue-Yang Road, Shanghai 200031, People's Republic of China.
authors.forename: Z F
authors.initials: ZF
authors.lastname: Wang
authors.forename: Y L
authors.initials: YL
authors.lastname: Shi
mesh_terms: D000818:Animals; D004365:Drugs, Chinese Herbal / Q000494:pharmacology*; D006624:Hippocampus / Q000187:drug effects / Q000378:metabolism; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology; D009466:Neuromuscular Blocking Agents / Q000494:pharmacology*; D018377:Neurotransmitter Agents / Q000378:metabolism*; D009924:Organ Culture Techniques; D015221:Potassium Channels / Q000187:drug effects* / Q000378:metabolism; D017729:Presynaptic Terminals / Q000187:drug effects* / Q000378:metabolism; D017966:Pyramidal Cells / Q000187:drug effects / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D009435:Synaptic Transmission / Q000187:drug effects*; D013997:Time Factors; D014315:Triterpenes
chemical_list: D004365:Drugs, Chinese Herbal; D009466:Neuromuscular Blocking Agents; D018377:Neurotransmitter Agents; D015221:Potassium Channels; C036454:toosendanin; D014315:Triterpenes