Go alpha regulates volatile anesthetic action in Caenorhabditis elegans

To identify genes controlling volatile anesthetic (VA) action, we have scre ened through existing Caenorhabditis elegans mutants and found that strains with a reduction in Go signaling are VA resistant. Loss-of-function mutant s of the gene goa-l, which codes for the alpha -subunit of Go, have EC(50)s for the VA isoflurane of 1.7- to 2.4-fold that of wild type. Strains overe xpressing egl-10, which codes for an RGS protein negatively regulating goa- l, are also isoflurane resistant. However, sensitivity to halothane, a stru cturally distinct VA, is differentially affected by Go pathway mutants. The RGS overexpressing strains, a goa-l missense mutant found to carry a novel mutation near the GTP-binding domain, and eat-16(rf) mutants, which suppre ss goa-1(gf) mutations, are all halothane resistant; gon-1(null) mutants ha ve wild-type sensitivities. Double mutant strains carrying mutations in bot h goa-l and unc-64, which codes for a neuronal syntaxin previously found to regulate VA sensitivity, show that the syntaxin mutant phenotypes depend i n part on goa-l expression. Pharmacological assays using the cholinesterase inhibitor aldicarb suggest that VAs and GOA-1 similarly downregulate choli nergic neurotransmitter release in C. elegans. Thus, the mechanism of actio n of VAs in C. elegans is regulated by Goa, and presynaptic Go alpha -effec tors are candidate VA molecular targets.