Monoaminergic Orchestration of Motor Programs in a Complex C. elegans Behavior
(A) Tyramine induces immobilization in a dose-dependent manner. Shown is the percentage of animals immobilized after 10 min on agar plates supplemented with tyramine. Wild-type animals become fully immobilized at concentrations above 30 mM tyramine, while ser-2 mutants continue sustained movement. Each data point represents the mean ± the standard error of the mean (SEM) for at least three trials, totaling a minimum of 30 animals. (B) G-protein signaling mutants are resistant to the paralytic of effects of exogenous tyramine. Shown is the percentage of animals that become immobilized after 10 min on 30 mM tyramine. Each bar represents the mean ± SEM for at least four trials totaling a minimum of 40 animals. (Inset) Schematic representation of the Gαo and Gαq signaling pathways that modulate locomotion in C. elegans. The genetic data suggest that SER-2 acts in the Gαo pathway. The names of the human orthologs are shown. Rescue denotes the transgenic line Pser-2::SER-2; ser-2(pk1357). (C, D) Tyramine affects locomotion and head movements through different mechanisms. Shown is the percentage of animals with sustained body (C) or head (D) movements on 30 mM tyramine. ser-2 mutants are partially resistant to the effects of tyramine on body movements, but not head movements. lgc-55 mutants continue to move their heads through the duration of the assay. Each data point represents the mean percentage of animals that become immobilized by tyramine each minute for 20 min ± SEM for at least six trials, totaling a minimum of 60 animals. Head movements were analyzed in an unc-3 mutant background. unc-3 mutants make few body movements but display normal head movements, and are wild-type for the ser-2 and lgc-55 loci. Statistical significance to wild-type: ***p<0.0001, two-tailed Student's t test. See also Figures S1 and S2.