Latest on 4-Aminopyridine (4-AP)

kenneth paul scholz kps2 at ellis.uchicago.edu
Sun May 16 16:53:08 EST 1993


In article <1993May15.194024.845 at ringer.cs.utsa.edu> senseman at lucy.brainlab.utsa.edu (David M. Senseman) writes:
>
>My question is this. Would 4-AP *increase* excitability of GABA neurons
>by depolarizing them alittle or *decrease* excitability of GABA neurons
>by depolarizing them alot or is this effect not a "GABA thing"?

4-AP is a classic blocker of the transient potassium current, which
is known to be a strong participant in controlling firing rate.  100 uM
4-AP would increase the firing rate of any neuron in which this current
participates.  To my knowledge, the actions of 4-AP do not involve
GABA in particular, I don't know why the description in the RBI catalog
is so specific for GABA-ergic neurons since 4-AP could increase
the excitability of many cell types.  4-AP probably also blocks other K+
currents, which might explain why it depolarizes some cells.  My guess
is that the increase in response you see is a result of increased
excitability resulting largely from block of the transient K+ 'A' current.


-- 
Ken Scholz                    Department of Pharm. and Physiology
kps2 at midway.uchicago.edu      Univ. of Chicago



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