Figure 1.
The isolated stomatogastric nervous system and the gastric mill circuit. A, The isolated stomatogastric nervous system consists of the stomatogastric ganglion (STG), oesophageal ganglion (OG), and paired commissural ganglia (CoGs) plus their connecting and peripheral nerves. All identified CoG projection neurons occur as single copies in each CoG. Each of the bilaterally symmetrical VCN mechanosensory systems projects through the vcn, dpon, and son to innervate the ipsilateral CoG. Arrows with dotted lines point to ganglia. Arrows with full lines point to nerves and identified projection neurons. B, Schematic of the identified MCN1 and CPN2 synaptic actions on the gastric mill neurons. MCN1 data were obtained from Coleman and Nusbaum (1994), Coleman et al. (1995), and Beenhakker (2004). CPN2 data were obtained from Norris et al. (1994). T-bars, synaptic excitation; filled circles, synaptic inhibition; resistor symbol, electrical coupling. Nerve labels (initalics) include the following: dgn, dorsal gastric nerve; dpon, dorsal posterior oesophageal nerve; ion, inferior oesophageal nerve; lgn, lateral gastric nerve; lvn, lateral ventricular nerve; mgn, medial gastric nerve; mvn, medial ventricular nerve; son, superior oesophageal nerve; stn, stomatogastric nerve; vcn, ventral cardiac nerve. Neuron labels include the following: AM, anterior median neuron; CPN2, commissural projection neuron 2; DG, dorsal gastric neuron; GM, gastric mill neuron; Int1, interneuron 1; LG, lateral gastric neuron; MCN1, 5, 7, modulatory commissural neuron 1, 5, 7; MG, medial gastric neuron; VCN, ventral cardiac neuron.