Expression of a glutamate-activated chloride current in Xenopus oocytes injected with Caenorhabditis elegans RNA: evidence for modulation by avermectin.
Membrane currents were recorded from Xenopus laevis oocytes injected with C. elegans poly(A)+ RNA. In such oocytes glutamate activated an inward membrane current that desensitized in the continued presence of glutamate. Glutamate-receptor agonists quisqualate, kainate, and N-methyl-D-aspartate were inactive. The reversal potential of the glutamate-sensitive current was -22 mV, and exhibited a strong dependence on external chloride with a 48 mV change for a 10-fold change in chloride. The chloride channel blockers flufenamate and picrotoxin inhibited the glutamate-sensitive current. Ibotenate, a structural analog of glutamate, also activated a picrotoxin-sensitive chloride current. Ibotenate was inactive when current was partially desensitized with glutamate, and the responses to low concentrations of glutamate and ibotenate were additive. The anthelmintic/insecticide compound avermectin directly activated the glutamate-sensitive current. In addition, avermectin increased the response to submaximal concentrations of glutamate, shifted the glutamate concentration-response curve to lower concentrations, and slowed the desensitization of glutamate-sensitive current. We propose that the glutamate-sensitive chloride current and the avermectin-sensitive chloride current are mediated via the same channel.
D000818:Animals; D000871:Anthelmintics / Q000494:pharmacology; D017173:Caenorhabditis elegans / Q000187:drug effects* / Q000235:genetics; D002463:Cell Membrane Permeability / Q000187:drug effects; D018118:Chloride Channels; D002712:Chlorides; D005971:Glutamates / Q000494:pharmacology*; D018698:Glutamic Acid; D007051:Ibotenic Acid / Q000494:pharmacology; D015640:Ion Channel Gating / Q000187:drug effects; D007559:Ivermectin / Q000031:analogs & derivatives / Q000494:pharmacology; D008565:Membrane Proteins / Q000187:drug effects*; D008845:Microinjections; D009865:Oocytes / Q000187:drug effects*; D011061:Poly A / Q000235:genetics*; D012313:RNA / Q000235:genetics*; D014982:Xenopus laevis
D000871:Anthelmintics; D018118:Chloride Channels; D002712:Chlorides; D005971:Glutamates; D008565:Membrane Proteins; D011061:Poly A; D007051:Ibotenic Acid; D018698:Glutamic Acid; D012313:RNA; D007559:Ivermectin; C019264:avermectin