We also found that GABA increased the gastric mill 4 (gm4) muscle excitatory junctional potential (EJP) while decreasing muscle fiber input resistance, indicating that the effect on contraction is mediated at least partially by presynaptic actions at the neuromuscular junction.
Moreover, it seems unlikely that GABAergic (or any other) modulation of gm4 by MPN would be physiologically relevant, since gm4 contracts during gastric mill rhythms, which themselves are suppressed by MPN activity (Blitz and Nusbaum, 1997, 1999).
borealis, the STG and portions of connecting nerves are located within the anterior aorta, one of the main arteries connecting to the heart (Maynard and Dando, 1974; Steinacker, 1978), and injection of neuroactive substances into the pericardial cavity, which is several centimeters from the stomach, has been shown to modify the activity of gastric mill neurons in lobsters (Heinzel, 1988; Turrigiano and Selverston, 1990).
Abbreviations: dgn, dorsal gastric nerve; dvn, dorsal ventricular nerve; EJP, excitatory junctional potential; GABA, [gamma]-aminobutyric acid; gm4, gastric mill 4 muscle; lvn, lateral ventricular nerve; LC/MS, reversed-phase liquid chromatography-mass spectrometry; MPN, modulatory proctolin neuron; POs, pericardial organs; STG.
Foregut having ossicles of the gastric mill, esophageal valve and other hard structure; total length 0.
The ossicles of the gastric mill are present, such as: mesocardiac, pterocardiac, zygocardiac (bearing the lateral teeth), urocardiac (bearing the tooth medial), propyloric, exopyloric and pyloric.
Cardiac chamber: gastric mill showing a group of well-developed articulated ossicles; cardiopyloric valve specialized bearing some denticles and several setae in the superior portion.
On the other hand, Kumlu (1999) related that the gastric mill is completely developed in the stomach of the mysis and these structures increase the carnivorous capacity of the larva, as well as the food retention and assimilation of energy.