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Nerve stimulation by E fi

LARS THOMSEN lars.thomsen at dkb.dk
Thu Nov 17 02:51:00 EST 1994


To : tvaughan at athena.mit.edu 

Stimulation of neurones

I had the same problem as you, I couldn't find anything anywhere
about the amount of current or voltage required to stimulate neurons.
I look everywhere, infact I found the very first article descriping the
technique of focal stimulation :

Coombs JR, Eccles JC, Fatt P, (1955)
The specific ionic conductances and their ionic movements across the
motorneuronal membrane that produce the inhibitory post-synaptic 
potential. J. Physiol (Lond) 130:326-373 
The reference is used in B. Hille "Ionic channels of excitable 
membranes"

Coombs et al used a double-electrode, one line for recording and one for 
stimulation. The normal way today (if you want to do intracellular 
recordings) is to have two separate electrodes. 

What you need to do stimulation in hairy skin is a constant current 
source driven by a huge potential source. I built one for use in in 
vitro measurements of enteric neurones of the porcine small intestine.

The device is working very good and it is delivering currents in the 
range 0.1-10 mA and in timeranges from 0.1-2 ms. It is driven by 32 9V
batteries = 288 V. This will in some circumstances not be a high enough 
voltage. 

So you need a CONSTANT CURRENT SOURCE, all electronic freaks know how to 
built one. 

MS Lars Thomsen
The Royal Veterinary & Agricultural University
Copenhagen Denmark

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