Developmental Loss of GABA- and Glycine-induced Depolarization and Ca2+ Transients in Embryonic Rat Dorsal Horn Neurons in Culture

Authors

  • Jian Wang,

    1. Department of Physiology and Cellular Biophysics and Center for Neurobiology and Behavior, Columbia University, 1106 Black Building, 630 W. 168th Street, New York, NY 10032, USA
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  • David B. Reichling,

    1. Department of Physiology and Cellular Biophysics and Center for Neurobiology and Behavior, Columbia University, 1106 Black Building, 630 W. 168th Street, New York, NY 10032, USA
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  • Andreas Kyrozis,

    1. Department of Physiology and Cellular Biophysics and Center for Neurobiology and Behavior, Columbia University, 1106 Black Building, 630 W. 168th Street, New York, NY 10032, USA
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  • Amy B. MacDermott

    Corresponding author
    1. Department of Physiology and Cellular Biophysics and Center for Neurobiology and Behavior, Columbia University, 1106 Black Building, 630 W. 168th Street, New York, NY 10032, USA
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Dr Amy MacDermott, as above

Abstract

More than 90% of dorsal horn neurons from embryonic day 15–16 rats responded to the inhibitory amino acids GABA and glycine by a transient elevation of intracellular Ca2+ concentration ([Ca2+]i) when maintained in culture for <1 week. This [Ca2+]i response has previously been shown to be due to depolarization and subsequent Ca2+ entry through voltage-gated Ca2+ channels following activation of bicuculline-sensitive GABAA receptors and strychnine-sensitive glycine receptors. Both the number of cells responding to GABA and glycine and the amplitude of the [Ca2+]i response diminished over time in culture. By 30 days in culture, none of the cells responded to GABA, muscimol or glycine by elevation of [Ca2+]i. The loss of the [Ca2+]i response was not due to a change in the abundance or the properties of voltage-gated Ca2+ channels, since over the same period of time dorsal horn neurons showed a large increase in the amplitude of the [Ca2+]i transient in response to 30 mM K+. Nor was the loss of the [Ca2+]i response due to a loss of GABA and glycine receptors. Instead, the decrease in the [Ca2+]i response over time paralleled a similar change in the electrophysiological responses. More than 90% of the neurons tested were depolarized in response to inhibitory amino acids during the first week in culture. After 30 days, all neurons tested responded to GABA and glycine with a hyperpolarization. These observations add support to the suggestion that GABA and glycine may excite dorsal horn neurons earlyin development and play a role in postmitotic differentiation.

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