Summary
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1.
Using intracellular staining and recording techniques in the ventral nerve cord of locusts, we have identified a pair of large interneurons which monosynaptically excite hindleg flexor and extensor tibiae motoneurons. The somata and input processes of these interneurons are in the mesothoracic ganglion and each makes its connections to hindleg motoneurons via a large axon running in the meso-metathoracic connective contralateral to its soma.
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We refer to these interneurons as C-neurons because single action potentials in one interneuron often caused the coactivation of the fast extensor tibiae motoneuron and a variable number of flexor tibiae motoneurons in one hindleg. The probability of activity in a C-neuron activating hindleg motoneurons depended on the position of the tibia, being highest when the tibia was flexed.
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Coactivation of the fast extensor tibiae motoneuron and a number of flexor motoneurons could also be elicited by a variety of stimuli in intact animals when the tibiae were close to full flexion. This resulted in the tibiae being locked into full flexion and, very often, to the initiation of the co-contraction phase of the jump. We refer to this synchronous activation of hindleg flexor and extensor motoneurons in intact animals as the cocking response.
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We propose that the C-neurons function to produce the cocking response. Consistent with this proposal is that the C-neurons receive input from all those sensory sources which evoke the cocking response.
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A general feature of the interneuronal organization in insects derived from this and other investigations is the existence of individual interneurons for the production of single aspects of a behavior. By controlling transmission of sensory information to motoneurons via these unique interneurons, the same sensory stimulus can evoke a variety of motor response. This concept is discussed in relation to the jumping system of the locust.
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Abbreviations
- DCMD :
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descending contralateral movement detector
- EMG :
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electromyogram
- FET :
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Fast extensor tibiae
References
Burrows M (1977) Flight mechanisms of the locust. In: Hoyle G (ed) Identified neurons and behavior of arthropods. Plenum Press, New York, pp 339–356
Heitler WJ (1974) The locust jump. Specializations of the metathoracic femoral-tibial joint. J Comp Physiol 89:93–104
Heitler WJ, Burrows M (1977a) The locust jump. I. The motor programme. J Exp Biol 66:203–220
Heitler WJ, Burrows M (1977b) The locust jump. II. Neural circuits of the motor programme. J Exp Biol 66:221–242
Pearson KG (1977) Interneurons in the ventral nerve cord of insects. In: Hoyle G (ed) Identified neurons and behavior of arthropods. Plenum Press, New York, pp 329–338
Pearson KG (1980) Burst generation in coordinating interneurons of the ventilatory system of the locust. J Comp Physiol 137:305–314
Pearson KG, Goodman CS (1981) Presynaptic inhibition of transmission from identified interneurons in the locust central nervous system. J Neurophysiol 45:501–515
Pearson KG, Heitler WJ, Steeves JD (1980) Triggering of locust jump by multimodal inhibitory interneurons. J Neurophysiol 43:257–278
Stewart WW (1978) Functional connections between cells revealed by dye-coupling with highly fluorescent naphthalamide tracer. Cell 14:741–759
Wilson JA (1979) The structure and function of serially homologous leg motor neurons in the locust. I. Anatomy. J Neurobiol 10:41–65
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We thank Dr. F. Delcomyn for his helpful comments on this manuscript and T. Abrams for valuable discussions in the initial phase of this investigation. The research was supported by a grant from the Canadian Medical Research Council.
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Pearson, K.G., Robertson, R.M. Interneurons coactivating hindleg flexor and extensor motoneurons in the locust. J. Comp. Physiol. 144, 391–400 (1981). https://doi.org/10.1007/BF00612571
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DOI: https://doi.org/10.1007/BF00612571