The innervation of the pyloric region of the crab,Cancer borealis: Homologous muscles in decapod species are differently innervated |
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Authors: | Scott L Hooper Michael B O'Neil Robert Wagner John Ewer Jorge Golowasch Eve Marder |
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Institution: | (1) Biology Department, Brandeis University, 02254 Waltham, Massachusetts, USA;(2) Present address: Laboratoire de Neurobiologie Comparée, CNRS, 33120 F-Arcachon, France |
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Abstract: | Summary The muscles of the pyloric region of the stomach of the crab,Cancer borealis, are innervated by motorneurons found in the stomatogastric ganglion (STG). Electrophysiological recording and stimulating techniques were used to study the detailed pattern of innervation of the pyloric region muscles. Although there are two Pyloric Dilator (PD) motorneurons in lobsters, previous work reported four PD motorneurons in the crab STG (Dando et al. 1974; Hermann 1979a, b). We now find that only two of the crab PD neurons innervate muscles homologous to those innervated by the PD neurons in the lobster,Panulirus interrruptus. The remaining two PD neurons innervate muscles that are innervated by pyloric (PY) neurons inP. interruptus. The innervation patterns of the Lateral Pyloric (LP), Ventricular Dilator (VD), Inferior Cardiac (IC), and PY neurons were also determined and compared with those previously reported in lobsters. Responses of the muscles of the pyloric region to the neurotransmitters, acetylcholine (ACh) and glutamate, were determined by application of exogenous cholinergic agonists and glutamate. The effect of the cholinergic antagonist, curare, on the amplitude of the excitatory junctional potentials (EJPs) evoked by stimulation of the pyloric motor nerves was measured. These experiments suggest that the differences in innervation pattern of the pyloric muscles seen in crab and lobsters are also associated with a change in the neurotransmitter active on these muscles. Possible implications of these findings for phylogenetic relations of decapod crustaceans and for the evolution of neural circuits are discussed.Abbreviations
ACh
acetylcholine
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Carb
carbamylcholine
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cpv
muscles of the cardio-pyloric valve
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cpv7n
nerve innervating muscle cpv7
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cv
muscles of the ventral cardiac ossicles
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cv1n
nerve innervating muscle cvl
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cv2n
nerve innervating muscle cv2
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EJP
excitatory junctional potential
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IC
inferior cardiac neuron
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IV
inferior ventricular neuron
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IVN
inferior ventricular nerve
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LP
lateral pyloric neuron
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LPG
lateral posterior gastric neuron
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lvn
lateral ventricular nerve
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mvn
medial ventricular nerve
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p
muscles of the pylorus
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PD
pyloric dilator neuron
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PD
in
intrinsic PD neuron
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PD
ex
extrinsic PD neuron
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pdn
pyloric dilator nerve
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PY
pyloric neuron
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pyn
pyloric nerve
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STG
stomatogastric ganglion
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VD
ventricular dilator neuron |
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