Miniature endplate currents

Involvement of the direct action on the endplate was indicated by the focal recording of miniature endplate currents (MEPCs) from frog. stutorius mu-sclc (Dcana and Scuka. 1990). Neostigmine at 3 fiM initially lengthened the decay phase of MEPCs and increased the amplitude of MEPCs probably due to ChE inhibition, but later it suppressed the amplitude and shortened the decay phase, suggesting a direct effect on the endplate. 

Kidokoro Y. and Nishikawa K.-I. 1994. Miniature endplate currents at the newly formed neuromuscular junction in Drosophila embryos and larvae. Neurosci. Res. 19 143-154. 

Histrionicotoxins antagonize both acetylcholine and glutamate-elicited excitation of central neurons (755), and have been cited as antagonizing glutamate-responses in invertebrate muscles (245). Histrionicotoxin also has a depressant effect on spontaneous activity of cortical and spinal neurons (114, 155). Perhydrohistrionicotoxin at very low concentrations (<0.1 pM) blocks endplate currents elicited by iontophoretic acetylcholine in rat neuromuscular preparations, while having no effect on spontaneous miniature endplate currents or endplate currents evoked by nerve stimulation (6, 14). Further studies will be required to clarify the reason for the remarkable potency of perhydrohistrionicotoxin versus responses to ionto-phoretically applied acetylcholine. 

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