JN Miami Valley Hospital
HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS
QUICK SEARCH:   [advanced]


     

J Neurophysiol 85: 43-53, 2001;
0022-3077/01 $5.00
This Article
Right arrow Full Text
Right arrow Full Text (PDF)
Right arrow Alert me when this article is cited
Right arrow Alert me if a correction is posted
Right arrow Citation Map
Services
Right arrow Email this article to a friend
Right arrow Similar articles in this journal
Right arrow Similar articles in ISI Web of Science
Right arrow Similar articles in PubMed
Right arrow Alert me to new issues of the journal
Right arrow Download to citation manager
Citing Articles
Right arrow Citing Articles via HighWire
Right arrow Citing Articles via ISI Web of Science (40)
Right arrow Citing Articles via Google Scholar
Google Scholar
Right arrow Articles by Prather, J. F.
Right arrow Articles by Cope, T. C.
Right arrow Search for Related Content
PubMed
Right arrow PubMed Citation
Right arrow Articles by Prather, J. F.
Right arrow Articles by Cope, T. C.

The Journal of Neurophysiology Vol. 85 No. 1 January 2001, pp. 43-53
Copyright ©2001 by the American Physiological Society

Amplification and Linear Summation of Synaptic Effects on Motoneuron Firing Rate

Jonathan F. Prather,1 Randall K. Powers,2 and Timothy C. Cope1

 1Department of Physiology, Emory University, Atlanta, Georgia 30322; and  2Department of Physiology and Biophysics, University of Washington, Seattle, Washington 98195

Prather, Jonathan F., Randall K. Powers, and Timothy C. Cope. Amplification and Linear Summation of Synaptic Effects on Motoneuron Firing Rate. J. Neurophysiol. 85: 43-53, 2001. The aim of this study was to measure the effects of synaptic input on motoneuron firing rate in an unanesthetized cat preparation, where activation of voltage-sensitive dendritic conductances may influence synaptic integration and repetitive firing. In anesthetized cats, the change in firing rate produced by a steady synaptic input is approximately equal to the product of the effective synaptic current measured at the resting potential (IN) and the slope of the linear relation between somatically injected current and motoneuron discharge rate (f-I slope). However, previous studies in the unanesthetized decerebrate cat indicate that firing rate modulation may be strongly influenced by voltage-dependent dendritic conductances. To quantify the effects of these conductances on motoneuron firing behavior, we injected suprathreshold current steps into medial gastrocnemius motoneurons of decerebrate cats and measured the changes in firing rate produced by superimposed excitatory synaptic input. In the same cells, we measured IN and the f-I slope to determine the predicted change in firing rate (Delta F = IN * f-I slope). In contrast to previous results in anesthetized cats, synaptically induced changes in motoneuron firing rate were greater-than-predicted. This enhanced effect indicates that additional inward current was present during repetitive firing. This additional inward current amplified the effective synaptic currents produced by two different excitatory sources, group Ia muscle spindle afferents and caudal cutaneous sural nerve afferents. There was a trend toward more prevalent amplification of the Ia input (14/16 cells) than the sural input (11/16 cells). However, in those cells where both inputs were amplified (10/16 cells), amplification was similar in magnitude for each source. When these two synaptic inputs were simultaneously activated, their combined effect was generally very close to the linear sum of their amplified individual effects. Linear summation is also observed in medial gastrocnemius motoneurons of anesthetized cats, where amplification is not present. This similarity suggests that amplification does not disturb the processes of synaptic integration. Linear summation of amplified input was evident for the two segmental inputs studied here. If these phenomena also hold for other synaptic sources, then the presence of active dendritic conductances underlying amplification might enable motoneurons to integrate multiple synaptic inputs and drive motoneuron firing rates throughout the entire physiological range in a relatively simple fashion.




This article has been cited by other articles:


Home page
 J. Neurophysiol.Home page
A. S. Hyngstrom, M. D. Johnson, and C. J. Heckman
Summation of Excitatory and Inhibitory Synaptic Inputs by Motoneurons With Highly Active Dendrites
J Neurophysiol, April 1, 2008; 99(4): 1643 - 1652.
[Abstract] [Full Text] [PDF]

Home page
 J. Physiol.Home page
C. J. Heckman, A. S. Hyngstrom, and M. D. Johnson
Active properties of motoneurone dendrites: diffuse descending neuromodulation, focused local inhibition
J. Physiol., March 1, 2008; 586(5): 1225 - 1231.
[Abstract] [Full Text] [PDF]

Home page
 J. Neurosci.Home page
M. Manuel, C. Meunier, M. Donnet, and D. Zytnicki
Resonant or Not, Two Amplification Modes of Proprioceptive Inputs by Persistent Inward Currents in Spinal Motoneurons
J. Neurosci., November 21, 2007; 27(47): 12977 - 12988.
[Abstract] [Full Text] [PDF]

Home page
 J. Neurophysiol.Home page
W. Zhou, Y. Xu, I. Simpson, and Y. Cai
Multiplicative Computation in the Vestibulo-Ocular Reflex (VOR)
J Neurophysiol, April 1, 2007; 97(4): 2780 - 2789.
[Abstract] [Full Text] [PDF]

Home page
 J. Neurophysiol.Home page
N. P. Cramer, Y. Li, and A. Keller
The Whisking Rhythm Generator: A Novel Mammalian Network for the Generation of Movement
J Neurophysiol, March 1, 2007; 97(3): 2148 - 2158.
[Abstract] [Full Text] [PDF]

Home page
 J. Neurophysiol.Home page
M. H. Schieber and G. Rivlis
Partial Reconstruction of Muscle Activity From a Pruned Network of Diverse Motor Cortex Neurons
J Neurophysiol, January 1, 2007; 97(1): 70 - 82.
[Abstract] [Full Text] [PDF]

Home page
 J. Neurophysiol.Home page
S. M. Jones and R. H. Lee
Fast Amplification of Dynamic Synaptic Inputs in Spinal Motoneurons In Vivo
J Neurophysiol, November 1, 2006; 96(5): 2200 - 2206.
[Abstract] [Full Text] [PDF]

Home page
 J. Neurophysiol.Home page
P. J. Harvey, Y. Li, X. Li, and D. J. Bennett
Persistent Sodium Currents and Repetitive Firing in Motoneurons of the Sacrocaudal Spinal Cord of Adult Rats
J Neurophysiol, September 1, 2006; 96(3): 1141 - 1157.
[Abstract] [Full Text] [PDF]

Home page
 J. Physiol.Home page
S. M. ElBasiouny, D. J. Bennett, and V. K. Mushahwar
Simulation of Ca2+ persistent inward currents in spinal motoneurones: mode of activation and integration of synaptic inputs
J. Physiol., January 15, 2006; 570(2): 355 - 374.
[Abstract] [Full Text] [PDF]

Home page
 J. Neurophysiol.Home page
S. M. ElBasiouny, D. J. Bennett, and V. K. Mushahwar
Simulation of Dendritic CaV1.3 Channels in Cat Lumbar Motoneurons: Spatial Distribution
J Neurophysiol, December 1, 2005; 94(6): 3961 - 3974.
[Abstract] [Full Text] [PDF]

Home page
 J. Neurosci.Home page
V. K. Haftel, E. K. Bichler, Q.-B. Wang, J. F. Prather, M. J. Pinter, and T. C. Cope
Central Suppression of Regenerated Proprioceptive Afferents
J. Neurosci., May 11, 2005; 25(19): 4733 - 4742.
[Abstract] [Full Text] [PDF]

Home page
 BrainHome page
M. A. Gorassini, M. E. Knash, P. J. Harvey, D. J. Bennett, and J. F. Yang
Role of motoneurons in the generation of muscle spasms after spinal cord injury
Brain, October 1, 2004; 127(10): 2247 - 2258.
[Abstract] [Full Text] [PDF]

Home page
 J. Neurophysiol.Home page
M. G. Maltenfort, M. L. McCurdy, C. A. Phillips, V. V. Turkin, and T. M. Hamm
Location and Magnitude of Conductance Changes Produced by Renshaw Recurrent Inhibition in Spinal Motoneurons
J Neurophysiol, September 1, 2004; 92(3): 1417 - 1432.
[Abstract] [Full Text] [PDF]

Home page
 J. Neurosci.Home page
C. B. Hart and S. F. Giszter
Modular Premotor Drives and Unit Bursts as Primitives for Frog Motor Behaviors
J. Neurosci., June 2, 2004; 24(22): 5269 - 5282.
[Abstract] [Full Text] [PDF]

Home page
 J. Neurophysiol.Home page
Y. Li, M. A. Gorassini, and D. J. Bennett
Role of Persistent Sodium and Calcium Currents in Motoneuron Firing and Spasticity in Chronic Spinal Rats
J Neurophysiol, February 1, 2004; 91(2): 767 - 783.
[Abstract] [Full Text] [PDF]

Home page
 J. Neurophysiol.Home page
A. M. Taylor and R. M. Enoka
Quantification of the Factors That Influence Discharge Correlation in Model Motor Neurons
J Neurophysiol, February 1, 2004; 91(2): 796 - 814.
[Abstract] [Full Text] [PDF]

Home page
 J. Neurophysiol.Home page
J. J. Kuo, R. H. Lee, M. D. Johnson, H. M. Heckman, and C. J. Heckman
Active Dendritic Integration of Inhibitory Synaptic Inputs In Vivo
J Neurophysiol, December 1, 2003; 90(6): 3617 - 3624.
[Abstract] [Full Text] [PDF]

Home page
 J. Neurophysiol.Home page
M. G. Maltenfort and R. E. Burke
Spindle Model Responsive to Mixed Fusimotor Inputs and Testable Predictions of beta Feedback Effects
J Neurophysiol, May 1, 2003; 89(5): 2797 - 2809.
[Abstract] [Full Text] [PDF]

Home page
 J. Neurophysiol.Home page
R. H. Lee, J. J. Kuo, M. C. Jiang, and C. J. Heckman
Influence of Active Dendritic Currents on Input-Output Processing in Spinal Motoneurons In Vivo
J Neurophysiol, January 1, 2003; 89(1): 27 - 39.
[Abstract] [Full Text] [PDF]

Home page
 J. Neurophysiol.Home page
R. K. Powers and M. D. Binder
Persistent Sodium and Calcium Currents in Rat Hypoglossal Motoneurons
J Neurophysiol, January 1, 2003; 89(1): 615 - 624.
[Abstract] [Full Text] [PDF]

Home page
 J. Neurophysiol.Home page
J. F. Prather, B. D. Clark, and T. C. Cope
Firing Rate Modulation of Motoneurons Activated by Cutaneous and Muscle Receptor Afferents in the Decerebrate Cat
J Neurophysiol, October 1, 2002; 88(4): 1867 - 1879.
[Abstract] [Full Text] [PDF]

Home page
 J. Neurophysiol.Home page
M. Gorassini, J. F. Yang, M. Siu, and D. J. Bennett
Intrinsic Activation of Human Motoneurons: Possible Contribution to Motor Unit Excitation
J Neurophysiol, April 1, 2002; 87(4): 1850 - 1858.
[Abstract] [Full Text] [PDF]

Home page
 J. Neurophysiol.Home page
V. K. Haftel, J. F. Prather, C. J. Heckman, and T. C. Cope
Recruitment of Cat Motoneurons in the Absence of Homonymous Afferent Feedback
J Neurophysiol, August 1, 2001; 86(2): 616 - 628.
[Abstract] [Full Text] [PDF]


HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS
Visit Other APS Journals Online