Summary
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1.
Intracellular stimulation of each of three different types of mechanoreceptors, the T, P and N cells, evokes swimming behavior in leech preparations. Stimulation of an individual N cell or P cell evoked swimming in 75% and 53% respectively, of the preparations tested. Stimulation of an individual T cell was ineffective in eliciting swimming; however, simultaneous stimulation of two T cells evoked swimming in 59% of our preparations.
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2.
Stimulation of mechanosensory neurons elicited swimming activity for a limited number of trials; i.e. the response habituated. The number of swim episodes evoked before habituation to criterion did not differ significantly for the different types of mechanoreceptors.
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3.
The duration of swim episodes declined significantly over the course of N cell stimulation. The tendency for swim length to decline with repeated stimulation was present as well for swim episodes elicited by P or T cell stimulation.
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4.
Swim initiation recovered spontaneously following habituation resulting from T cell stimulation. Spontaneous recovery following N cell stimulation was not demonstrated. However, N cell stimulation evoked swimming again after DP nerve shock or to a limited extent, after cell 204 stimulation. Spontaneous recovery of swim initiation to P cell stimulation was not investigated.
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5.
A previous study detailed habituation of swimming activity to mechanical stimulation of the body wall (Debski and Friesen 1985). Only the T cells are activated significantly by this stimulus. Stimulation of sensory receptors other than mechanoreceptors was not effective in eliciting swimming in our preparation. We conclude that T cells mediate swim initiation elicited by stroking of the body wall and that the cessation of swimming to this stimulus is not due to sensory adaptation.
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Debski, E.A., Friesen, W.O. Intracellular stimulation of sensory cells elicits swimming activity in the medicinal leech. J. Comp. Physiol. 160, 447–457 (1987). https://doi.org/10.1007/BF00615078
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DOI: https://doi.org/10.1007/BF00615078