Fig. 5. Double-stained immunohistochemistry of serotonin (red) and synaptotagmin (green). (A) In intact larva, serotonin was synthesized at the apical ganglion (red) and synaptotagmin-possessed nerve cell network lined along the ciliary band (green). (B) In pCPA-treated larva, the apical ganglion did not produce serotonin, but formation of the synaptotagmin-possessing nerve cell network (green) was not affected (B). Bar, 100 µm.