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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. 2010; 56(6): 22-30


Effect of 4-aminopyridine-sensitive potassium current on high frequency tonic firing of the rat retinal ganglion cells

Kuznetsov KI, Maslov VIu, Fedulova SA, Veselovs'kyĭ MS

  1. O.O.Bogomoletz Institute of Physiology, National Academy of Sciences of Ukraine, Kyiv, Ukraine
  2. International Center Molecular Physiology, National Academy of Sciences of Ukraine, Kyiv, Ukraine
DOI: https://doi.org/10.15407/fz56.06.022

Abstract

High frequency firing properties of the rat retinal ganglion cells and role of 4-AP-sensitive potassium current in firing generation were studied using whole cell patch-clamp tech­niques. Potassium channel blocker 4-AP (0,2 mM) reduced depolarization-evoked firing rate by 62% (from 50 ± 5, n = 12 to 19 ± 2 Hz, n = 7). Single action potential parameters were affected: half-width was increased by 133% (from 1,2 ± 0,1, n = 12 to 2,8 ± 0,3 ms, n = 7), decay slope was decreased by 63% (from 102 ± 11, n = 12 to 38 ± 7 mV/ms, n = 7) and afterhyperpolarization amplitude by 83% (from 18 ± 2, n = 12 to 3 ± 2 mV, n = 7). 4-AP application (0,2 mM) reduced po­tassium current amplitude of the retinal neurons. 4-AP-sensi­tive current was obtained by digital subtraction of current that was registered in the presence of the blocker from control current records (1,61 ± 0,22 nA, n = 6). 4-AP-sensitive current was equal to 0,40 ± 0,09 nA (n = 6). Thus, moderate (25%) reducing of potassium current amplitude leads to essential changes in firing properties of retinal neurons. 4-AP-sensitive residual current was similar to Kv3.1/Kv3.2 potassium currents that were described in literature previously. Moreover, we excluded the possibility of 4-AP influence on Kv1 channels by specific blocker a-dendrotoxin (100 nM) application. Such applications significantly affected neither firing frequency nor single action potential parameters. The data obtained suggest that 4-AP-sensitive current plays a key role in high frequency firing generation in the rat retinal ganglion cells. We assume that the 4-AP-sensitive current is mediated by Kv3.1/Kv3.2 conductance.

Keywords: retinal ganglion cell, high frequency tonic firing, 4-AP

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