Morphological and electrophysiological aspects of dorsal median paired neurons generating plateau action potentials in the terminal abdominal ganglion of the insect central nervous system |
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Authors: | C Amat B Hue |
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Institution: | (1) Laboratoire de Neurophysiologie, CNRS ERS 108, Université d' Angers, rue Haute de Reculée, F-49045 Angers Cedex, France |
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Abstract: | Among the three clusters of dorsal unpaired median neurons of the Periplaneta americana terminal abdominal ganglion, another type of neuron has been characterized by anterograde cobalt stainings and microelectrode technique. These neurons are bilaterally distributed in the ganglion. Their axons ipsilaterally exit the ganglion via the anterior proctodeal nerves, to innervate the proctodeum. They are characterized by a long-duration overshooting action potentials and a low firing frequency. Most often the depolarizing phase is composed of two peaks: a fast spike followed by a slow phase. Tetrodotoxin suppressed the fast peak and blocked the spontaneous activity suggesting that sodium channels are involved in the depolarizing phase as well as in the initiation of the action potential. Calcium channel blockers induced a disappearing of the slow depolarizing phase indicating the participation of calcium ions and a reduction of the afterhyperpolarization reflecting the participation of calcium-activated potassium channels. Furthermore, cadmium, as lanthanum or barium, induced a long-lasting plateau potential, which would be due to a persistent sodium conductance. Tetraethylammonium increased the duration of the action potential indicating that potassium channels are implicated in the falling phase. The results demonstrate that these neurons are different from other cells, especially dorsal unpaired median neurons, of the central nervous system of the cockroach.Abbreviations
DUM
dorsal unpaired median
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SDP
slow depolarizing phase
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AP
action potential
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PAP
plateau action potential
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TAG
terminal abdominal ganglion
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CNS
central nervous system |
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Keywords: | Dorsal median paired neuron Plateau action potential Central nervous system Insect Periplaneta americana |
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