Elsevier

Comparative Biochemistry and Physiology

Volume 12, Issue 4, August 1964, Pages 509-516, IN7-IN11, 517-525
Comparative Biochemistry and Physiology

Interneurons commanding swimmeret movements in the crayfish, Procambarus clarki (girard)

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Abstract

  • 1.

    1. Five interneurons causing bilateral rhytmic swimmeret movements when stimulated are described with their localizations in the cross-section of the cord between thorax and abdomen.

  • 2.

    2. At about 30 stimuli per sec the resulting rhythm is equivalent to that present during natural beats. Below 20 and above 100 stimuli per sec no rhythmic movements are obtained.

  • 3.

    3. As during endogenously caused rhythmicity, the swimmerets of the fifth ganglion are the first to respond. When the fifth ganglion is removed, discharges are first elicited in the first roots of the fourth ganglion, and similarly in those of the third, when the fourth is absent. No rhythmic discharges are caused in the second and first ganglion, when no posterior ganglia are present.

  • 4.

    4. The rhythmicity elicited by three of the five command fibers is indistinguishable. The other two give slightly different responses, one a more sustained one, the other a somewhat slower rhythm.

  • 5.

    5. At frequencies of stimulation away from the “optimal” (30/sec), a longer delay is observed before the first burst occurs when below, a shorter delay when above this frequency. The conduction time in the anterior direction between ganglia is not influenced, but the repetition rate of the bursts is higher with increased frequencies.

  • 6.

    6. Hemisections of the cord, involving one connective, have no influence on the ensuing bursts in any of the roots, when made in the anterior part of the cord.

  • 7.

    7. Hemisections between the third, fourth and fifth ganglia result in a dependency on the laterality of the cut. When ipsilateral to the command fiber, such cuts prevent beating in the roots posterior to the cut, but not when made contralateral.

  • 8.

    8. At least three different interneurons which inhibit the rhythmic motor discharges of both sides were shown to be present.

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This work was supported by grants from the National Science Foundation (G-17655) and U.S. Public Health Service (NB-03627).

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