| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
|
|
|
|||||||
|
|||||||||
1. Intracellular iontophoretic injections of EGTA (5--20 nA) into cat spinal motoneurones consistently greatly reduce the amplitude of the delayed after hyperpolarization (a.h.p.) that follows the spike. 2. This effect is accompanied by a large reduction (on average by 3/4) in the marked increase in input conductance normally associated with the a.h.p. 3. There is also a consistent, though less regular, tendency for the resting input conductance to decrease (on average by 1/5), as well as some depolarization. 4. Recovery of the a.h.p., the associated conductance increase and the resting conductance is ver slow. It is sometimes accelerated by injections of citrate and Cl-, or CA2+. 5. Other hyperpolarizing phenomena, such as recurrent or othodromically-evoked i.p.s.p.s, are not depressed by injections of EGTA. 6. When depolarization is minimal EGTA injections that markedly depress the a.h.p. do not affect the rate of rise or fall of the spike. If, as a result of depolarization, an early a.h.p. is visible, it is patently insensitive to EGTA. 7. The post-spike depolarizing after-potential (delayed depolarization) is not obviously affected by EGTA, apart from the usual diminution seen during depolarization. 8. Since the main action of EGTA is to bind free Ca2+, the marked depression of the a.h.p. indicates that the sharp increase in K conductance which generates the a.h.p. is probably caused by a influx of Ca2+ accompanying the action potential. It is suggested that this inward Ca2+ current may be manifested in the depolarizing after-potential.
This article has been cited by other articles:
|
|
 |
|
  M. Manuel, C. Meunier, M. Donnet, and D. Zytnicki The afterhyperpolarization conductance exerts the same control over the gain and variability of motoneurone firing in anaesthetized cats J. Physiol., November 1, 2006; 576(3): 873 - 886. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 M. Manuel, C. Meunier, M. Donnet, and D. Zytnicki How Much Afterhyperpolarization Conductance Is Recruited by an Action Potential? A Dynamic-Clamp Study in Cat Lumbar Motoneurons J. Neurosci., September 28, 2005; 25(39): 8917 - 8923. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 Y. Nishimura, M. Asahi, K. Saitoh, H. Kitagawa, Y. Kumazawa, K. Itoh, M. Lin, T. Akamine, H. Shibuya, T. Asahara, et al. Ionic Mechanisms Underlying Burst Firing of Layer III Sensorimotor Cortical Neurons of the Cat: An In Vitro Slice Study J Neurophysiol, August 1, 2001; 86(2): 771 - 781. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
K. E. Jones and P. Bawa Computer Simulation of the Responses of Human Motoneurons to Composite 1A EPSPS: Effects of Background Firing Rate J Neurophysiol, January 1, 1997; 77(1): 405 - 420. [Abstract] [Full Text] [PDF]
|
|
| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
