期刊
JOURNAL OF NEUROPHYSIOLOGY
卷 113, 期 2, 页码 537-549出版社
AMER PHYSIOLOGICAL SOC
DOI: 10.1152/jn.00907.2013
关键词
bifurcation; dynamic clamp; ion channel density; pyramidal neuron; threshold dynamics
资金
- Swedish Research Council (VR) Grant [15083]
- Karolinska Institutet Faculty funds
- Biotechnology and Biological Sciences Research Council (BBSRC)
- European Commission
- Swedish Society of Medicine
Several types of intrinsic dynamics have been identified in brain neurons. Type 1 excitability is characterized by a continuous frequency-stimulus relationship and, thus, an arbitrarily low frequency at threshold current. Conversely, Type 2 excitability is characterized by a discontinuous frequency-stimulus relationship and a nonzero threshold frequency. In previous theoretical work we showed that the density of K-v channels is a bifurcation parameter, such that increasing the K-v channel density in a neuron model transforms Type 1 excitability into Type 2 excitability. Here we test this finding experimentally, using the dynamic clamp technique on Type 1 pyramidal cells in rat cortex. We found that increasing the density of slow K-v channels leads to a shift from Type 1 to Type 2 threshold dynamics, i.e., a distinct onset frequency, subthreshold oscillations, and reduced latency to first spike. In addition, the action potential was resculptured, with a narrower spike width and more pronounced afterhyperpolarization. All changes could be captured with a two-dimensional model. It may seem paradoxical that an increase in slow K channel density can lead to a higher threshold firing frequency; however, this can be explained in terms of bifurcation theory. In contrast to previous work, we argue that an increased outward current leads to a change in dynamics in these neurons without a rectification of the current-voltage curve. These results demonstrate that the behavior of neurons is determined by the global interactions of their dynamical elements and not necessarily simply by individual types of ion channels.
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