| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH |
|
|
|
|||||||
|
|||||||||
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
1 Psychiatry, Program in Neuroscience, Washington University, St. Louis, Missouri, United States
2 Washington University School of Med, United States; Psychiatry, Washington University School of Med, St. Louis, Missouri, United States
* To whom correspondence should be addressed. E-mail: menneris{at}psychiatry.wustl.edu.
Thin, unmyelinated axons densely populate the mammalian hippocampus and cortex. However, the location and dynamics of spike initiation in thin axons remain unclear. We investigated basic properties of spike initiation and propagation in CA3 neurons of juvenile rat hippocampus. Sodium channel alpha subunit distribution and local applications of tetrodotoxin demonstrate that the site of first threshold crossing in CA3 neurons is approximately 35 µm distal to the soma, somewhat more proximal than our previous estimates. This discrepancy can be explained by the finding, obtained with simultaneous whole-cell somatic and extracellular axonal recordings, that a zone of axon stretching to approximately 100 µm distal to the soma reaches a maximum rate of depolarization nearly synchronously by the influx of sodium from the high-density channels. Models of the proximal axon incorporating observed distributions of sodium channel staining recapitulated salient features of somatic and axonal spike waveforms, including the predicted initiation zone, characteristic spike latencies, and conduction velocity. The preferred initiation zone was unaltered by stimulus strength or repetitive spiking, but repetitive spiking increased threshold and significantly slowed initial segment recruitment time and conduction velocity. Our work defines the dynamics of initiation and propagation in hippocampal principal cell axons and may help reconcile recent controversies over initiation site in other axons.
This article has been cited by other articles:
|
|
 |
|
  A. Lorincz and Z. Nusser Cell-Type-Dependent Molecular Composition of the Axon Initial Segment J. Neurosci., December 31, 2008; 28(53): 14329 - 14340. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 J. F. Atherton, D. L. Wokosin, S. Ramanathan, and M. D. Bevan Autonomous initiation and propagation of action potentials in neurons of the subthalamic nucleus J. Physiol., December 1, 2008; 586(23): 5679 - 5700. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 M. Royeck, M.-T. Horstmann, S. Remy, M. Reitze, Y. Yaari, and H. Beck Role of Axonal NaV1.6 Sodium Channels in Action Potential Initiation of CA1 Pyramidal Neurons J Neurophysiol, October 1, 2008; 100(4): 2361 - 2380. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
G. J. Kress, M. J. Dowling, J. P. Meeks, and S. Mennerick High Threshold, Proximal Initiation, and Slow Conduction Velocity of Action Potentials in Dentate Granule Neuron Mossy Fibers J Neurophysiol, July 1, 2008; 100(1): 281 - 291. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
C. Schmidt-Hieber, P. Jonas, and J. Bischofberger Action potential initiation and propagation in hippocampal mossy fibre axons J. Physiol., April 1, 2008; 586(7): 1849 - 1857. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
J. N. Mercer, C. S. Chan, T. Tkatch, J. Held, and D. J. Surmeier Nav1.6 Sodium Channels Are Critical to Pacemaking and Fast Spiking in Globus Pallidus Neurons J. Neurosci., December 5, 2007; 27(49): 13552 - 13566. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
L. L. Scott, T. A. Hage, and N. L. Golding Weak action potential backpropagation is associated with high-frequency axonal firing capability in principal neurons of the gerbil medial superior olive J. Physiol., September 1, 2007; 583(2): 647 - 661. [Abstract] [Full Text] [PDF]
|
|
| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH |
| Visit Other APS Journals Online |
