Fig. 8. Diagram of the C. borealis cardiac ganglion with neuromodulators present in the pericardial organs. The excitatory actions (+) of peptides, serotonin, dopamine and presumably acetylcholine on the cardiac ganglion [CG; GAHKNYLRFa data were studied in Cruz-Bermudez et al. (Cruz-Bermudez et al., 2006)]. The peptide AST-3 and GABA are both potent inhibitors (–) of the CG output. Other modulators such as histamine and octopamine did not induce statistically significant changes on the CG motor pattern and were classified as weak or ineffective modulators. Large ovals, motor neurons; small ovals, pacemaker cells.