Differential blocking of myelinated nerve fibres by transient depolarization
- 74 Downloads
Conduction was blocked in the large myelinated fibres (Group II) of a cutaneous nerve by applying a transient polarizing current to the nerve. By appropriately adjusting the polarizing current conduction was not affected in most of the thin myelinated fibres (Group III) when all group II fibres were blocked. This selective action was achieved in 11 out of 15 experiments. Thus the method enables afferent volleys to be set up selectively in Group III fibres.
Recording single unit action potentials from the nerve revealed that the Group II compound volley is a reliable indicator for the extent of the block. As a prerequisite for this finding it was established by unit analysis that temporal dispersion due to the polarizing current did not occur within both Groups II and III fibre populations.
The membrane mechanism of the block was examined by testing the excitability changes in single fibres produced by the polarizing current. The findings indicate that the block was achieved by a membrane depolarization, causing inactivation of the sodium system.
Asynchronous firing produced by the blocking current itself, known to be a disturbing factor in such experiments, was shown to be virtually absent during the block. Discharges in Group II fibres evoked by the initial rise of the depolarizing current were prevented from conditioning the CNS effects of the selective Group III volley by appropriately advancing the onset of the current.
A complete and selective Group II block could also be performed during prolonged stimulation. In particular the method was shown to be able to ensure afferent activity being confined to small fibres during adequate stimulation of skin receptors.
Key wordsMyelinated Nerve Fibres Selective Afferent Stimulation Nerve Block by Transient Polarization
Unable to display preview. Download preview PDF.
- Bishop, G. H., Heinbecker, P.: The afferent functions of non-myelinated or “C”-Fibers. Amer. J. Physiol.114, 179–193 (1935).Google Scholar
- Boyd, J. A., Davey, M. R.: Composition of peripheral nerves, pp. 1–57. Edinburgh-London: E & S Livingstone LTD, 1968.Google Scholar
- Bromm, B., Frankenhaeuser, B.: Repetitive discharge of the excitable membrane computed on the basis of voltage clamp data for the node of Ranvier. Pflügers Arch.332, 21–27 (1972).Google Scholar
- Brown, A. G., Hamann, W. C.: DC-polarization and impulse conduction failure in mammalian nerve fibres. J. Physiol. (Lond.)222, 66–67 P (1972).Google Scholar
- Brown, A. G., Iggo, A.: A quantitative study of cutaneous receptors and afferent fibres in the cat and rabbit. J. Physiol. (Lond.)193, 707–733 (1967).Google Scholar
- Cangiano, A., Lutzemberger, L.: The action of selectively activated Group II muscle afferent fibers on extensor motoneurons. Brain Res.41, 475–478 (1972).Google Scholar
- Casey, K. L., Blick, M.: Observations on anodal polarization of cutaneous nerve. Brain Res.13, 155–167 (1969).Google Scholar
- Clark, D., Hughes, J., Gasser, H. S.: Afferent function in the group of nerve fibers of slowest conduction velocity. Amer. J. Physiol.114, 69–76 (1935).Google Scholar
- Dawson, G. D., Merrill, E. G., Wall, P. D.: Dorsal root potentials produced by stimulation of fine afferents. Science167, 1385–1387 (1970).Google Scholar
- Douglas, W. W., Malcolm, J. L.: The effect of localized cooling on conduction in cat nerves. J. Physiol. (Lond.)130, 53–71 (1955).Google Scholar
- Dudel, J.: The effect of polarizing current on action potential and transmitter release in crayfish motor nerve terminals. Pflügers Arch.324, 227–248 (1971).Google Scholar
- Franz, D. N., Iggo, A.: Conduction failure in myelinated and non-myelinated axons at low temperatures. J. Physiol. (Lond.)199, 319–345 (1968).Google Scholar
- Gasser, H. S., Erlanger, J.: The role of fiber size in establishment of a nerve block by pressure or by cocaine. Amer. J. Physiol.88, 581–591 (1929).Google Scholar
- Graham, H. T.: Supernormality, a modification of the recovery process in nerve. Amer. J. Physiol.110, 225 (1934).Google Scholar
- Gregor, M., Zimmermann, M.: Dorsal root potentials produced by afferent volleys in cutaneous Group III fibres. J. Physiol. (Lond.) (in press) (1973).Google Scholar
- Guz, A., Trenchard, D. W.: The role of non-myelinated vagal afferent fibres from the lungs in the genesis of tachypnoea in the rabbit. J. Physiol. (Lond.)213, 345–371 (1971).Google Scholar
- Handwerker, H. O., Sassen, M.: Contribution of naturally stimulated D- and G-hair receptors to the excitation of cortical SI-neurons. Pflügers Arch.334, 310–326 (1972).Google Scholar
- Handwerker, H. O., Zimmermann, M.: Cortical evoked responses upon selective stimulations of cutaneous Group III fibers and the mediating spinal pathways. Brain Res.36, 437–440 (1972).Google Scholar
- Hodgkin, A. L.: Evidence for electrical transmission in nerve. Parts I and II. J. Physiol. (Lond.)90, 183–232 (1937).Google Scholar
- Hodgkin, A. L., Huxley, A. F.: A quantitative description of membrane current and its application to conduction and excitation in nerve. J. Physiol. (Lond.)117, 500–544 (1952).Google Scholar
- Hodgkin, A. L., Rushton, W. A. H.: The electrical constants of a crustacean nerve fibre. Proc. roy. Soc. B133, 444–479 (1946).Google Scholar
- Jänig, W., Zimmermann, M.: Presynaptic depolarization of myelinated afferent fibres evoked by stimulation of cutaneous C fibres. J. Physiol. (Lond.)214, 29–50 (1971).Google Scholar
- Koll, W., Haase, J., Schütz, R. M., Mühlberg, B.: Reflexentladungen der tiefspinalen Katze durch afferente Impulse aus hochschwelligen nociceptiven A-Fasern (post ·-Fasern) und aus nociceptiven C-Fasern cutaner Nerven. Pflügers Arch. ges. Physiol.272, 270–289 (1961).Google Scholar
- Kuffler, S. W., Vaughan Williams, E. M.: Small nerve functional potentials. The distribution of small motor nerves to frog skeletal muscle, and the membrane characteristics of the fibres they innervate. J. Physiol. (Lond.)121, 289–317 (1953).Google Scholar
- Manfredi, M.: Differential block of conduction of larger fibres in peripheral nerve by direct current. Arch. ital. Biol.108, 52–71 (1970).Google Scholar
- Mendell, L. M., Wall, P. D.: Presynaptic hyperpolarization: a role for fine afferent fibres. J. Physiol. (Lond.)172, 274–294 (1964).Google Scholar
- Paintal, A. S.: Block of conduction in mammalian myelinated nerve fibres by low temperatures. J. Physiol. (Lond.)180, 1–19 (1965).Google Scholar
- Rudin, D. O., Eisenman, G.: After-potential of spinal axons in vivo. J. gen. Physiol.36, 643–657 (1953).Google Scholar
- Schmidt, R. F., Senges, J., Zimmermann, M.: Excitability measurements at the central terminals of single mechano-receptor afferents during slow potential changes. Exp. Brain Res.3, 220–233 (1967).Google Scholar
- Stämpfli, R.: Bau und Funktion isolierter markhaltiger Nervenfasern. Ergebn. Physiol.47, 70–165 (1952).Google Scholar
- Wall, P. D.: Excitability changes in afferent fibre terminations and their relation to slow potentials. J. Physiol. (Lond.)142, 1–21 (1958).Google Scholar
- Zimmermann, M.: Selective activation of C-fibers. Pflügers Arch. ges. Physiol.301, 329–333 (1968).Google Scholar
- Zimmermann, M.: Contribution by thin myelinated (Group III) cutaneous afferent fibres to central nervous activity as revealed by selective stimulation. J. Physiol. (Lond.)224, 33–34P (1972).Google Scholar