Summary
Control of the crayfish uropod motoneurons by the unilateral-type local non-spiking interneurons (LNSNs) in the terminal (sixth) abdominal ganglion was studied with intracellular recording and current injection.
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1.
Current injected into LNSNs affected the spike activity of uropod motoneurons in a graded manner. The effects depended on both the duration and the intensity of current pulses.
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2.
Simultaneous intracellular recordings from an LNSN and an opener motoneuron showed that LNSNs could change the motoneuron membrane potential by their own membrane potential change without generating spikes.
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3.
In fifty-nine cases, we penetrated LNSNs which affected uropod motoneurons bidirectionally. Hyperpolarization of 23 LNSNs decreased and that of other 36 LNSNs increased the spontaneous discharge rate of an identified reductor exopodite motoneuron (Red MN) No. 1. Depolarization had the opposite effect in either case.
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4.
It is suggested that at least one chemical synapse should be intercalated between the LNSN and the motoneuron. although whether their connection is monosynaptic or not still remains open to future study.
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5.
Twenty-four penetrated LNSNs co-actively controlled the synergistic set of motoneurons. Other 23 LNSNs also controlled the antagonistic set in addition to the synergistic set of motoneurons in a reciprocal way, and other 21 LNSNs in a co-activating way.
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6.
The possible role of unilateral-type LNSNs in the motor control, especially in the non-rhythmical, episodic movement such as uropod steering, is discussed.
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Abbreviations
- LNSN :
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local non-spiking interneuron
- Red MN :
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reductor exopodite motoneuron
- Add MN :
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adductor exopodite motoneuron
- Abd Ex :
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abductor exopodite
- p.s.p. :
-
postsynaptic potential
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Nagayama, T., Takahata, M. & Hisada, M. Functional characteristics of local non-spiking interneurons as the pre-motor elements in crayfish. J. Comp. Physiol. 154, 499–510 (1984). https://doi.org/10.1007/BF00610164
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DOI: https://doi.org/10.1007/BF00610164