Neurotransmission
Acetylcholine (ACh) is the primary excitatory neurotransmitter in nematodes. Release of ACh at the neuromuscular junction will increase the rate of spikes (action potentials, Figure 22.18). Inhibitory fibers release gamma-aminobutyric acid (GABA), that hyperpolarizes the muscle to decrease the action potentials.
Other neuropeptides have been discovered, but their functions remain unknown at present. Serotonin has been found and may work in conjunction with ACh and neuropeptides to control and modulate feeding activities.