stomatogastric ganglion

The stomatogastric ganglion (STG) is a small neuronal structure in crustaceans containing approximately 30 neurons that form two central pattern generator circuits: the gastric mill circuit and the pyloric circuit. The STG controls the striated muscles of the gastric mill and pyloric regions of the crustacean stomach and is a major model system in the study of neural circuit function and neuromodulation.

In crustaceans such as Cancer borealis and Homarus americanus, the stomatogastric ganglion is located on the dorsal surface of the foregut (stomach), within the stomatogastric nervous system. It receives input via the stomatogastric nerve from the paired commissural ganglia and sends motor output through the ventricular nerves to the stomach muscles.

The stomatogastric ganglion is involved in generating and coordinating the rhythmic motor patterns that drive the movements of the gastric mill and pyloric stomach in crustaceans. Its ~30 neurons form two central pattern generators that produce the gastric mill rhythm for food grinding and the pyloric rhythm for food filtering, under the influence of extensive neuromodulatory input.

In experimental contexts, isolation from modulatory input—by stomatogastric nerve transection—may be associated with quiescence of the gastric mill circuit and stereotyping of the pyloric rhythm. Pharmacological application of amines, peptides, and other neuromodulators to the STG is associated with diverse changes in circuit output. Temperature changes and ionic manipulation are also associated with altered STG activity.

The STG is extensively studied using electrophysiological techniques in semi-intact and dissected preparations. Intracellular sharp electrode and patch-clamp recordings allow characterization of individual neuron properties. Extracellular suction electrode recordings from ventricular nerves monitor circuit output. Immunohistochemistry and confocal microscopy reveal the expression of neurotransmitters, neuropeptides, and ion channels in STG neurons.