Dopaminergic responses in the STNS are mediated by Gs, Gi, and Gq in all species of Decapod crustaceans examined. (a) Phylogenetic classification scheme for Decapod crustaceans modified from (Dixon et al. 2003). Branches are not drawn to scale. (b) DA activates Gs, Gi and Gq in all species examined. G protein activity in the absence (open bar) versus the presence (filled bar) of 10−5mol/L DA was measured for Gs, Gi, and Gq in STNS membrane preparations from multiple species, as indicated. For each species, the total number of animals used for all experiments, and the total number of independent experiments are: 25 Penaeus, n = 5 experiments; 13 Machrobrachium, n = 3; 30 Panulirus, n = 17; 10 Homarus, n = 7; 20 Callinectes, n = 5. The activities of all three G proteins were measured in each experiment. Data are represented as the mean ± SEM. Statistically significant differences in the activity of a given G protein are indicated with an asterisk (*) (p < 0.05). For Gq activity in Callinectes, p < 0.051 and for Gs activity in Machrobrachium, p < 0.07.