The electromotor system of the stargazer: A model for integrative actions at electrotonic synapses

Michael V. L. Bennett, G. D. Pappas

Research output: Contribution to journalArticle

6 Citations (Scopus)

Abstract

The electric organs of Astroscopus are modified from extraocular muscles and innervated by the enlarged oculomotor nuclei. The electromotor neuron somata are contacted by fine processes with which they form gap junctions. Presynaptic vesicles and active zones are also present, although physiological data give no indication of chemically mediated transmission. Antidromic stimulation produces long lasting graded depolarizations in the electromotor neurons. The latency is sufficiently short to indicate that the cells are electrotonically coupled, which was confirmed by direct measurement. Antidromic invasion may normally fail and is easily blocked by hyperpolarization revealing initial segment and axon spikes. Spinal stimulation evokes poststynaptic potentials (PSPs) and orthodromic impulses; the PSPs are not smoothly graded in amplitude. A medullary nucleus innervates the electromotor nucleus; the medullary cells also show short latency graded antidromic depolarizations and presumably are electrotonically coupled. Their coupling accounts for the variability in PSPs evoked by spinal stimulation. Apparent time constants differ greatly for direct stimulation of a single cell, decay of afterhyperpolarization, electrotonic spread from one cell to a neighbor, and decay of PSPs and graded antidromic depolarizations. The differences can be accounted for in terms of a highly interconnected network of electrotonically coupled cells, which was simulated computationally. Because of the long membrane time constant graded antidromic depolarizations summate. Because antidromic invasion is facilitated by depolarization, the antidromic depolarizations can show pronounced facilitation. The observed 'plasticity' within this electrotonically coupled system provides a model for integrative actions at other sites of coupling.

Original languageEnglish (US)
Pages (from-to)748-761
Number of pages14
JournalJournal of Neuroscience
Volume3
Issue number4
StatePublished - 1983

Fingerprint

Electrical Synapses
Oculomotor Muscles
Electric Organ
Neurons
Gap Junctions
Carisoprodol
Evoked Potentials
Membranes

ASJC Scopus subject areas

  • Neuroscience(all)

Cite this

The electromotor system of the stargazer : A model for integrative actions at electrotonic synapses. / Bennett, Michael V. L.; Pappas, G. D.

In: Journal of Neuroscience, Vol. 3, No. 4, 1983, p. 748-761.

Research output: Contribution to journalArticle

@article{aae338fe3e93482287427bb9c130ea4f,
title = "The electromotor system of the stargazer: A model for integrative actions at electrotonic synapses",
abstract = "The electric organs of Astroscopus are modified from extraocular muscles and innervated by the enlarged oculomotor nuclei. The electromotor neuron somata are contacted by fine processes with which they form gap junctions. Presynaptic vesicles and active zones are also present, although physiological data give no indication of chemically mediated transmission. Antidromic stimulation produces long lasting graded depolarizations in the electromotor neurons. The latency is sufficiently short to indicate that the cells are electrotonically coupled, which was confirmed by direct measurement. Antidromic invasion may normally fail and is easily blocked by hyperpolarization revealing initial segment and axon spikes. Spinal stimulation evokes poststynaptic potentials (PSPs) and orthodromic impulses; the PSPs are not smoothly graded in amplitude. A medullary nucleus innervates the electromotor nucleus; the medullary cells also show short latency graded antidromic depolarizations and presumably are electrotonically coupled. Their coupling accounts for the variability in PSPs evoked by spinal stimulation. Apparent time constants differ greatly for direct stimulation of a single cell, decay of afterhyperpolarization, electrotonic spread from one cell to a neighbor, and decay of PSPs and graded antidromic depolarizations. The differences can be accounted for in terms of a highly interconnected network of electrotonically coupled cells, which was simulated computationally. Because of the long membrane time constant graded antidromic depolarizations summate. Because antidromic invasion is facilitated by depolarization, the antidromic depolarizations can show pronounced facilitation. The observed 'plasticity' within this electrotonically coupled system provides a model for integrative actions at other sites of coupling.",
author = "Bennett, {Michael V. L.} and Pappas, {G. D.}",
year = "1983",
language = "English (US)",
volume = "3",
pages = "748--761",
journal = "Journal of Neuroscience",
issn = "0270-6474",
publisher = "Society for Neuroscience",
number = "4",

}

TY - JOUR

T1 - The electromotor system of the stargazer

T2 - A model for integrative actions at electrotonic synapses

AU - Bennett, Michael V. L.

AU - Pappas, G. D.

PY - 1983

Y1 - 1983

N2 - The electric organs of Astroscopus are modified from extraocular muscles and innervated by the enlarged oculomotor nuclei. The electromotor neuron somata are contacted by fine processes with which they form gap junctions. Presynaptic vesicles and active zones are also present, although physiological data give no indication of chemically mediated transmission. Antidromic stimulation produces long lasting graded depolarizations in the electromotor neurons. The latency is sufficiently short to indicate that the cells are electrotonically coupled, which was confirmed by direct measurement. Antidromic invasion may normally fail and is easily blocked by hyperpolarization revealing initial segment and axon spikes. Spinal stimulation evokes poststynaptic potentials (PSPs) and orthodromic impulses; the PSPs are not smoothly graded in amplitude. A medullary nucleus innervates the electromotor nucleus; the medullary cells also show short latency graded antidromic depolarizations and presumably are electrotonically coupled. Their coupling accounts for the variability in PSPs evoked by spinal stimulation. Apparent time constants differ greatly for direct stimulation of a single cell, decay of afterhyperpolarization, electrotonic spread from one cell to a neighbor, and decay of PSPs and graded antidromic depolarizations. The differences can be accounted for in terms of a highly interconnected network of electrotonically coupled cells, which was simulated computationally. Because of the long membrane time constant graded antidromic depolarizations summate. Because antidromic invasion is facilitated by depolarization, the antidromic depolarizations can show pronounced facilitation. The observed 'plasticity' within this electrotonically coupled system provides a model for integrative actions at other sites of coupling.

AB - The electric organs of Astroscopus are modified from extraocular muscles and innervated by the enlarged oculomotor nuclei. The electromotor neuron somata are contacted by fine processes with which they form gap junctions. Presynaptic vesicles and active zones are also present, although physiological data give no indication of chemically mediated transmission. Antidromic stimulation produces long lasting graded depolarizations in the electromotor neurons. The latency is sufficiently short to indicate that the cells are electrotonically coupled, which was confirmed by direct measurement. Antidromic invasion may normally fail and is easily blocked by hyperpolarization revealing initial segment and axon spikes. Spinal stimulation evokes poststynaptic potentials (PSPs) and orthodromic impulses; the PSPs are not smoothly graded in amplitude. A medullary nucleus innervates the electromotor nucleus; the medullary cells also show short latency graded antidromic depolarizations and presumably are electrotonically coupled. Their coupling accounts for the variability in PSPs evoked by spinal stimulation. Apparent time constants differ greatly for direct stimulation of a single cell, decay of afterhyperpolarization, electrotonic spread from one cell to a neighbor, and decay of PSPs and graded antidromic depolarizations. The differences can be accounted for in terms of a highly interconnected network of electrotonically coupled cells, which was simulated computationally. Because of the long membrane time constant graded antidromic depolarizations summate. Because antidromic invasion is facilitated by depolarization, the antidromic depolarizations can show pronounced facilitation. The observed 'plasticity' within this electrotonically coupled system provides a model for integrative actions at other sites of coupling.

UR - http://www.scopus.com/inward/record.url?scp=0020612206&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=0020612206&partnerID=8YFLogxK

M3 - Article

C2 - 6834104

AN - SCOPUS:0020612206

VL - 3

SP - 748

EP - 761

JO - Journal of Neuroscience

JF - Journal of Neuroscience

SN - 0270-6474

IS - 4

ER -