Summary
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1.
Spikeless communication between dendrites of crayfish motoneurons was demonstrated by intracellular current injection.
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2.
Subthreshold depolarization of one motoneuron (Add MN) innervating the adductor exopodite, one of the closer muscles of the uropod, increased the spontaneous discharge rate of another motoneuron (Red MN No. 1) innervating another closer muscle, reductor exopodite.
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3.
Hyperpolarization of the Add MN caused a decrease in the spike frequency of the Red MN No. 1.
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4.
The effects are graded and dependent on the membrane potential changes in the current-injected cells.
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5.
Spikeless communication was also observed between opener motoneurons. Such communication was observed only between synergistic motoneurons and not between antagonistic ones.
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6.
Regions in the Add MN in which current injection effectively changed the Red MN's activity were always distant from the spike-initiating region, and confined to the distal dendritic branches.
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7.
The amplitude of e.p.s.p.s recorded from the Red MN No. 1 in response to antidromic spikes of the Add MN was increased by hyperpolarization and decreased by depolarization at the site of recording. The spikeless, graded interaction appears to be mediated by chemical transmission via a monosynaptic connection.
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8.
It is concluded that the crayfish uropod motoneurons function not only as simple output elements but also as complex integrative elements by forming local circuits at restricted dendritic regions.
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Abbreviations
- Add MN :
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adductor exopodite motoneuron
- Red MN :
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reductor exopodite motoneuron
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Nagayama, T., Takahata, M. & Hisada, M. Local spikeless interaction of motoneuron dendrites in the crayfishProcambarus clarkii girard. J. Comp. Physiol. 152, 335–345 (1983). https://doi.org/10.1007/BF00606239
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DOI: https://doi.org/10.1007/BF00606239