One GABA and two acetylcholine receptors function at the C. elegans neuromuscular junction


We describe an electrophysiological preparation of the neuromuscular junction of the nematode C. elegans, which adds to its considerable genetic and genomic resources. Mutant analysis, pharmacology and patch-clamp recording showed that the body wall muscles of wild-type animals expressed a GABA receptor and two acetylcholine receptors. The muscle GABA response was abolished in animals lacking the GABA receptor gene unc-49. One acetylcholine receptor was activated by the nematocide levamisole. This response was eliminated in mutants lacking either the unc-38 or unc-29 genes, which encode alpha and non-alpha acetylcholine receptor subunits, respectively. The second, previously undescribed, acetylcholine receptor was activated by nicotine, desensitized rapidly and was selectively blocked by dihydro-β-erythroidine, thus explaining the residual motility of unc-38 and unc-29 mutants. By recording spontaneous endogenous currents and selectively eliminating each of these receptors, we demonstrated that all three receptor types function at neuromuscular synapses.

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Figure 1: C. elegans neuromuscular preparation.
Figure 2: Voltage-gated potassium and calcium currents are present in body wall muscles.
Figure 3: A functional GABA receptor is expressed in the muscle and encoded by the unc-49 gene.
Figure 4: The levamisole-sensitive current is abolished in unc-38(e264) and unc-29(e1072) mutants.
Figure 5: A nicotine-sensitive, rapidly desensitizing acetylcholine receptor is expressed in the muscle.
Figure 6: The nicotine-sensitive acetylcholine receptor is selectively blocked by the nicotinic antagonist dihydro-β-erythroidine (DHβE, 5 μM).
Figure 7: All three receptors are functionally active at the synapse.


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The authors thank K. Broadie, T. Fergestad and D.E. Featherstone for technical assistance, L. Avery and A.V. Maricq for discussions, M. Hammarlund for providing the F21D12.3-GFP strain, K. Knobel for confocal images and K. Broadie and D.E. Featherstone for reading the manuscript. This work was supported by NIH grant RO3 MHS9820-01 (J.E.R.) and the Damon Runyon Fund (E.M.J.).

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Correspondence to Janet E. Richmond.

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Richmond, J., Jorgensen, E. One GABA and two acetylcholine receptors function at the C. elegans neuromuscular junction. Nat Neurosci 2, 791–797 (1999).

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