pH Dependence of transmission at electronic synapses of the crayfish septate axon

A. Campos de Carvalho, David C. Spray, Michael V. L. Bennett

Research output: Contribution to journalArticle

18 Citations (Scopus)

Abstract

Gap junctions between segments of the crayfish septate axon mediate electronic transmission of impulses propagating along the length of the nerve cord. We simultaneously measured intracellular pH (pHi) and gap junctional conductance (gj) while axons were exposed to saline equilibrated with CO2, weak acids, and the weak base ammonium chloride. Normal pHi is about 7.1. When pHi is elevated, gj is unaffected. When pHi is reduced, gj declines with an apparent pK of about 6.7 and a Hill coefficient of about 2.7. We also measured effects of pHi on non-junctional conductance (gnj) and on the coupling coefficient, k. Over the pHi range 6.2-8, gnj increases approximately linearly with pHi. Since k is a function of gj and gnj, it reached a maximum at about pHi 7.1, decreasing at higher and lower pHi. The pHi dependence of gj in crayfish septate axon is less steep and has a lower apparent pK than the gj-pHi relation in two vertebrate embryos previously examined. This finding illustrates a difference in gating among analoguos and possibly homologous membrane channels.

Original languageEnglish (US)
Pages (from-to)279-286
Number of pages8
JournalBrain Research
Volume321
Issue number2
DOIs
StatePublished - Nov 12 1984

Fingerprint

Astacoidea
Synapses
Axons
Ammonium Chloride
Gap Junctions
Ion Channels
Vertebrates
Embryonic Structures
Acids

Keywords

  • electrotonic synapse
  • gap junction
  • pH uncoupling
  • septate axon

ASJC Scopus subject areas

  • Developmental Biology
  • Molecular Biology
  • Clinical Neurology
  • Neuroscience(all)

Cite this

pH Dependence of transmission at electronic synapses of the crayfish septate axon. / Campos de Carvalho, A.; Spray, David C.; Bennett, Michael V. L.

In: Brain Research, Vol. 321, No. 2, 12.11.1984, p. 279-286.

Research output: Contribution to journalArticle

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N2 - Gap junctions between segments of the crayfish septate axon mediate electronic transmission of impulses propagating along the length of the nerve cord. We simultaneously measured intracellular pH (pHi) and gap junctional conductance (gj) while axons were exposed to saline equilibrated with CO2, weak acids, and the weak base ammonium chloride. Normal pHi is about 7.1. When pHi is elevated, gj is unaffected. When pHi is reduced, gj declines with an apparent pK of about 6.7 and a Hill coefficient of about 2.7. We also measured effects of pHi on non-junctional conductance (gnj) and on the coupling coefficient, k. Over the pHi range 6.2-8, gnj increases approximately linearly with pHi. Since k is a function of gj and gnj, it reached a maximum at about pHi 7.1, decreasing at higher and lower pHi. The pHi dependence of gj in crayfish septate axon is less steep and has a lower apparent pK than the gj-pHi relation in two vertebrate embryos previously examined. This finding illustrates a difference in gating among analoguos and possibly homologous membrane channels.

AB - Gap junctions between segments of the crayfish septate axon mediate electronic transmission of impulses propagating along the length of the nerve cord. We simultaneously measured intracellular pH (pHi) and gap junctional conductance (gj) while axons were exposed to saline equilibrated with CO2, weak acids, and the weak base ammonium chloride. Normal pHi is about 7.1. When pHi is elevated, gj is unaffected. When pHi is reduced, gj declines with an apparent pK of about 6.7 and a Hill coefficient of about 2.7. We also measured effects of pHi on non-junctional conductance (gnj) and on the coupling coefficient, k. Over the pHi range 6.2-8, gnj increases approximately linearly with pHi. Since k is a function of gj and gnj, it reached a maximum at about pHi 7.1, decreasing at higher and lower pHi. The pHi dependence of gj in crayfish septate axon is less steep and has a lower apparent pK than the gj-pHi relation in two vertebrate embryos previously examined. This finding illustrates a difference in gating among analoguos and possibly homologous membrane channels.

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