QUICK SEARCH:   [advanced] Author: Keyword(s):
Home     Help     Feedback     Subscriptions     Archive     Search     Table of Contents

This Article Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by MAGURA, I. S. Articles by ZAMEKHOVSKY, I. Z. Search for Related Content PubMed Articles by MAGURA, I. S. Articles by ZAMEKHOVSKY, I. Z.

Journal of Experimental Biology 59,767-780 (1973)
Published by Company of Biologists 1973

Repetitive Firing in Molluscan Giant Neurones

I. S. MAGURA ¹ and I. Z. ZAMEKHOVSKY ¹

¹ Department of General Physiology of Nervous System, Bogomoletz Institute of Physiology, Academy of Sciences, Kiev-24, 252601, U.S.S.R.

1. The repetitive responses of molluscan neurones to steady injected outward current have been examined using intracellular microelectrodes. Voltage-clamp experiments were also performed to investigate the participation of transport mechanisms for potassium current in neurones during firing.

2. The maximum rate of rise of action potentials usually decreases during repetitive firing. Simultaneously an increasing duration of the falling phase of spikes is observed. The peak level of spikes in most cases is relatively stable if external Ca²⁺ concentration exceeds 3-4 mM.

3. The peak level of action potentials markedly decreases during firing in solutions with low Ca²⁺ concentration. A similar effect is observed if the Ca²⁺ ions in normal Ringer solution are completely replaced by Mg²⁺ ions.

4. With increasing external Ca²⁺ concentration the maximum rate of rise of action potentials becomes more stable during repetitive firing.

5. With increasing external Ca²⁺ concentration the steady-state inactivation of fast transient potassium channels is removed. Increase in Ca²⁺ concentration (in range from 10-40 mM) is roughly equivalent to a hyperpolarization of 7-8 mV.

6. Experiments with TEA show that in some neurones of Limnea stagnalis the last transient potassium channels participate in carrying potassium current during the falling phase of the action potentials at the beginning of repetitive firing.

7. The role of potassium inactivation as well as of Ca²⁺ ions in mechanisms which stabilize the peak level of action potentials during repetitive firing is discussed.