We investigated the EGL-30 (Gqalpha) pathway in C. elegans by using genetic screens to identify genes that confer phenotypes similar to egl-30 mutants. One such gene, egl-8, encodes a phospholipase Cbeta that is present throughout the nervous system and near intestinal cell junctions. EGL-30 and EGL-8 appear to positively regulate synaptic transmission because reducing their function results in strong aldicarb resistance and slow locomotion rates. In contrast, GOA-1 (Goalpha) and DGK-1 (diacylglycerol kinase) appear to negatively regulate synaptic transmission, because reducing their function results in strong aldicarb hypersensitivity and hyperactive locomotion. A genetic analysis suggests that GOA-1 negatively regulates the EGL-30 pathway and that DGK-1 antagonizes the EGL-30 pathway.