Journal of comparative physiology

, Volume 143, Issue 4, pp 541–553

Electrophysiological and morphological characterization of the winter flounder mauthner cell

  • Steven J. Zottoli
Article

DOI: 10.1007/BF00609920

Cite this article as:
Zottoli, S.J. J. Comp. Physiol. (1981) 143: 541. doi:10.1007/BF00609920

Summary

Flatfish (Pseudopleuronectes americanus) have Mauthner cells (M-cells) which are small as compared to certain other teleosts and behaviorally these fish display a suppression of a M-cell initiated startle response while on the substrate. They may depend on camouflage and, therefore, immobility in protection from predation. This ability to suppress the startle response could then be expressed in membrane properties of the M-cell, inhibition of the motoneurons innervated by M-axon collaterals or visual, tactile, auditory and vestibular inputs to the M-cell. Thus the present experiments were designed to study some electrophysiological and morphological properties of the winter flounder M-cell for comparison with that of the goldfish.

Morphologically the winter flounder M-cell is similar to that of the goldfish. Specifically it has two major dendrites, is located at the level of the VIIIth nerve, has an axon that decussates to the opposite side of the medulla and has an axon cap. The latter structure is similar in its organization to that of the goldfish, a finding which contradicts previous reports (Figs. 8–10).

Electrophysiological identification of the winter flounder M-cell was complicated by the similarity of its antidromic response latency to that of other adjacent neurons. In addition, the frequent failure of the antidromically activated spike to invade the M-cell initial segment-axon hillock region resulted in small field potentials recorded in the axon cap. Rather, the cell was localized utilizing orthodromic fields generated by stimulation of the VIIIth nerve or more commonly with an ‘extrinsic hyperpolarizing potential’ which is localized to the axon cap (Fig. 2). Intracellular records of membrane potential, inhibitory potentials (Fig. 4) and VIIIth nerve EPSPs (Fig. 5) were similar to those described in the goldfish. However, the saccular input, which in goldfish is auditory in nature, most likely is responsive to postural changes in the adult flatfish and would have little influence on M-cell excitability in response to an abrupt sound stimulus. This postulated reduction of excitatory input may be one factor contributing to the suppression of sound-evoked startle responses when the winter flounder is on a compatible background.

Abbreviations

M-cell

Mauthner cell

PHP

passive hyperpolarizing potential

EHP

extrinsic hyperpolarizing potential

LCI

late collateral inhibition

Copyright information

© Springer-Verlag 1981

Authors and Affiliations

  • Steven J. Zottoli
    • 1
    • 2
    • 3
  1. 1.Marine Biological LaboratoryWoods HoleUSA
  2. 2.Division of NeurobiologyState University of New York at BuffaloBuffaloUSA
  3. 3.Research Institute on AlcoholismBuffaloUSA
  4. 4.Department of BiologyWilliams CollegeWilliamstownUSA

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