Ishihara et al. have studied how neuronal circuits manage integration of multiple signals in Caenorhabditis elegans, whose simple nervous system contains 302 neurons. Wild-type animals are attracted to the odorant diacetyl and repulsed by Cu2+. Normally, avoidance of Cu2+ can be suppressed by the presence of diacetyl, but, in hen-1 mutants, diacetyl was less effective in luring the animals across a barrier of Cu2+. In the absence of Cu2+, hen-1 mutants were equally sensitive to the attractant properties of diacetyl, but hen-1 mutants were less sensitive than wild-type animals to Cu2+ as an inhibitor of chemotaxis toward diacetyl. Thus, the defect seems to lie in the association of the two signals. In a second behavioral assay using NaCl and starvation, hen-1 mutants were again less sensitive to interacting signals. The HEN-1 protein appears to be a secreted protein and may function as a neuromodulator, like the peptide FMRFamide. — LBR
Cell109, 639 (2002).