Summary
-
1.
An investigation was made into the presynaptic depolarization of the spinal cord terminals of mechanoreceptor units of the hind foot of the cat after short mechanical displacement of the skin. The depolarization was measured by testing the excitability of the primary afferent fibres.
-
2.
The following types of mechanoreceptor units were investigated: touch receptors of the central foot pad, hair follicle receptors, and touch corpuscles of the hairy skin. They were all depolarized by mechanical stimuli to the central pad or to the hairy skin. No difference has been found between receptor units which had or did not have a collateral in the dorsal columns.
-
3.
The amount of depolarization depended on the amplitude of the mechanical stimulus. With weak mechanical pulses there was a close relation between the amplitude of the pulse and the size of the depolarization, but there was little additional increase of the depolarization with skin indentations exceeding 10 to 15 μ. No spatial facilitation could be demonstrated when two mechanical pulses were applied simultaneously.
-
4.
The presynaptic depolarization of cutaneous mechanoreceptor afferents has a ‘surround’ pattern of organization: with mechanical pulses of constant amplitude the depolarization was largest when the pulse was applied at or close to the receptive field of the unit and decreased with increasing distance between the middle of the receptive field and the stimulus point. It seemed unimportant whether or not the unit under study was excited by the conditioning stimulus.
-
5.
There is a discussion of the functional significance of these findings.
This is a preview of subscription content, log in via an institution to check access.
Similar content being viewed by others
References
Andersen, P., J.C. Eccles, R.F. Schmidt and T. Yokota: Slow potential waves produced in the cuneate nucleus by cutaneous volleys and by cortical stimulation. J. Neurophysiol. 27, 78–91 (1964a).
— and T. Yokota: Depolarization of presynaptic fibers in the cuneate nucleus. J.Neurophysiol. 27, 92–106 (1964b).
—: Presynaptic inhibitory action of cerebral cortex on the spinal cord. Nature (Lond.) 194, 740–743 (1962).
— Cortically evoked depolarization of primary afferent fibers in the spinal cord. J. Neurophysiol. 27, 63–77 (1964).
Armett, C. J., J.A.B. Gray, R.W. Hunsperger and S. Lal: The transmission of information in primary receptor neurones and second-order neurones of a phasic system. J. Physiol. (Lond.) 164, 395–421 (1962).
Carpenter, D., I. Engberg and A. Lundberg: Presynaptic inhibition in the lumbar cord evoked from the brain stem. Experientia 18, 450–451 (1962).
—: Effects from the pyramidal tract on primary afferents and on spinal reflex actions to primary afferents. Experientia 18, 337–338 (1962).
— Primary afferent depolarization evoked from the sensorimotor cortex. Acta physiol. scand. 59, 126–142 (1963).
Darian-Smith, J.: Presynaptic component in the afferent inhibition observed within trigeminal brain-stem nuclei of the cat. J. Neurophysiol. 28. 695–709 (1965).
Devanandan, M.S., R.M. Eccles and T. Yokota: Muscle stretch and the presynaptic inhibition of the group Ia pathway to motoneurones. J. Physiol. (Lond.) 179, 430–441 (1965).
Eccles, J.C., R.M. Eccles and F. Magni: Central inhibitory action attributable to presynaptic depolarization produced by muscle afferent volleys. J. Physiol. (Lond.) 159, 147–166 (1961).
—: Central pathways responsible for depolarization of primary afferent fibres. J. Physiol. (Lond.) 161, 237–257 (1962a).
— Presynaptic inhibition of the central action of flexor reflex afferents. J. Physiol. (Lond.) 161, 258–281 (1962b).
—: Potential changes recorded inside primary afferent fibres within the spinal cord. J. Physiol. (Lond.) 149, 250–273 (1959).
—: Depolarization of central terminals of Group I afferent fibres from muscle. J. Physiol. (Lond.) 160, 62–93 (1962).
—: Depolarization of central terminals of Group I b afferent fibers from muscle. J. Neurophysiol. 26. 1–27 (1963a).
— The location and the mode of action of the presynaptic inhibitory pathways on to Group I afferent fibers from muscle. J. Neurophysiol. 26, 506–522 (1963b).
— Depolarization of the central terminals of cutaneous afferent fibers. J. Neurophysiol. 26, 646–661 (1963c).
Eccles, R.M., B. Holmqvist and P.E. Voorhoeve: Presynaptic inhibition from contralateral cutaneous afferent fibres. Acta physiol. scand. 62, 464–473 (1964a).
— Presynaptic depolarization of cutaneous afferents by volleys in contralateral muscle afferents. Acta physiol. scand. 62, 474–484 (1964b).
Frank, K.: Basic mechanisms of synaptic transmission in the central nervous system. I.R.E. Trans, med. Electr. ME-6, 85–88 (1959).
—: Presynaptic and postsynaptic inhibition of monosynaptic reflexes. Fed. Proc. 16, 39–40 (1957).
Fuller, D.R., and J.A.B. Gray: The relation between mechanical displacements applied to a cat's pad and the resultant impulse patterns. J. Physiol. (Lond.) 182, 465–483 (1966).
Hunt, C.C., and A.K. McIntyre: An analysis of fibre diameter and receptor characteristics of myelinated cutaneous afferent fibres in cat. J. Physiol. (Lond.) 153, 99–112 (1960).
Schmidt, R.F., J. Senges, u. M. Zimmermann: Untersuchungen zur funktionellen Bedeutung der präsynaptischen Hemmung von Mechano-Afferenzen im Rückenmark. Pflügers Arch. ges. Physiol. 289, R32 (1966).
— Excitability measurements of the central terminals of single mechanoreceptor afferents during slow potential changes. Exp. Brain Res. 3, 220–233 (1967).
—: Dorsal root potentials evoked by natural stimulation of antaneous afferents. Nature (Lond.) 212, 522–523 (1966).
—, M.E. Vogel, u. M. Zimmermann: Langsame Potentiale im Nucleus gracilis der Katze. Pflügers Arch. ges. Physiol. 291, R4 (1966).
—, W.D. Willis: Intracellular recording from motoneurones of the cervical spinal cord of the cat. J. Neurophysiol. 26, 28–43 (1963).
Wall, P.D.: Excitability changes in afferent fibre terminations and their relation to slow potentials. J. Physiol. (Lond.) 142, 1–21 (1958).
Author information
Authors and Affiliations
Additional information
This work was supported by the Deutsche Forschungsgemeinschaft.
Rights and permissions
About this article
Cite this article
Schmidt, R.F., Senges, J. & Zimmermann, M. Presynaptic depolarization of cutaneous mechanoreceptor afferents after mechanical skin stimulation. Exp Brain Res 3, 234–247 (1967). https://doi.org/10.1007/BF00235587
Received:
Issue Date:
DOI: https://doi.org/10.1007/BF00235587