Abstract
A developmental change in the ionic basis of the inward current of action potentials has been observed in many excitable cells1. In cultured spinal neurones of Xenopus, the timing of the development of the action parallels that seen in vivo2,3. In vitro, as in vivo, neurones initially produce action potentials of long duration which are principally Ca-dependent; after 1 day of development the impulse is brief and primarily Na-dependent3–5. At both ages, however, both inward components are present4–6 and the mechanism underlying shortening of the action potential is unknown. One possibility is that the outward currents change during development. Using the patch-clamp technique7, we have recorded single K+-channel currents in membrane patches isolated from the cell bodies of cultured embryonic neurones3. The unitary conductance of one class of K+ channels was ∼155 pS and depolarization increased the probability of a channel being open. Neither conductance nor voltage dependence seemed to change with time in culture; in contrast, the Ca2+-sensitivity of this K+ channel increased. In younger neurones, Ca2+-sensitivity was greatly reduced or absent, whereas in more mature neurones, the activity of this channel was Ca-dependent. Such a change could account for the shortening of the action potential duration by increasing the relative contribution of outward currents.
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Blair, L., Dionne, V. Developmental acquisition of Ca2+-sensitivity by K+ channels in spinal neurones. Nature 315, 329–331 (1985). https://doi.org/10.1038/315329a0
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DOI: https://doi.org/10.1038/315329a0
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