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ISSN 2522-9028 (Print)
ISSN 2522-9036 (Online)
DOI: https://doi.org/10.15407/fz

Fiziologichnyi Zhurnal

is a scientific journal issued by the

Bogomoletz Institute of Physiology
National Academy of Sciences of Ukraine

Editor-in-chief: V.F. Sagach

The journal was founded in 1955 as
1955 – 1977 "Fiziolohichnyi zhurnal" (ISSN 0015 – 3311)
1978 – 1993 "Fiziologicheskii zhurnal" (ISSN 0201 – 8489)
1994 – 2016 "Fiziolohichnyi zhurnal" (ISSN 0201 – 8489)
2017 – "Fiziolohichnyi zhurnal" (ISSN 2522-9028)

Fiziol. Zh. 2007; 53(3): 61-69


Prolonged after-potentialsof myelinated nervous fibres ofamphibian after blockage of potas-sium channels by 4-aminopyridine

I.V. Kuznetzova, D.A. Evstigneev, N.V. Gluhova.

    Ecological Foundation, Ulianov Region, Russia


Abstract

Myelinated nerve fibres of Rana ridibunda Pallas were studied by using extra-cellular recording technique. 4-aminopyridine, a blocker of fast potassium channels produced considerable changes in duration of the after-depolarization and increase in total membrane depolarization (evaluated by an action poten- tial area). These effects were time-dependent. The after-depo- larization duration under 4-aminopyridine (4-AP) treatment changes in 3 phases: at the beginning of the exposure its dura- tion increased; then the increase stopped; and later duration of the after-depolarization start to decrease. The last phase was often followed by hyperpolarizing after-potential. The inter- change of these phases accompanies by statistically signifi- cant increase of the action potential area (from 189.201 ± 28.437 mVЧms in normal solution to 489.945 ± 41.75 mVЧms in 5 minutes after 4-AP application). These observations are explained as a result of the increased activation of the slow potassium channels and decreased portion of fast potassium channels involved in membrane repolarization. The decrease in post-tetanic depolarization duration, the appearance of the post-tetanic hyperpolarization at low frequencies and increase of post-tetanic hyperpolarization at higher frequencies of stimulation under 4-AP treatment are dependent on activation of slow potassium channels.

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