Latest on 4-Aminopyridine (4-AP)

David M. Senseman senseman at lucy.brainlab.utsa.edu
Sat May 15 14:40:24 EST 1993

We have using multiple site optical recording techniques to monitor
retinohypothalamic tract (RHT) stimulation of the hamster 
suprachiasmatic nucleus (SCN). Yesterday we got around to looking
at the effects of 100 uM 4-AP on the evoked response. 4-AP caused
at *dramatic* increase (100%) in the amplitude of the optically
recorded response. According to the RBI catalog, 4-AP is suppose
to "depolarize GABA neurons" and be a weak, non-selective K+ blocker.

I should also mention that 20 uM bicuculine in this preparation 
*decreases* the amplitude of the evoke response.

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"?


David M. Senseman, Ph.D.              | Imagine the Creator as a low 
(senseman at lonestar.utsa.edu)          | comedian, and at once the world 
Life Sciences Visualization Lab       | becomes explicable.
University of Texas at San Antonio    |               H.L. Mencken 

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