Current pump used by voltage-clamp method

By using the voltage-clamp method we 
can record the end-plate current which reflects
 changes in the conductance of the subsynaptic
membrane during neuromuscular transmission. The classic (plain) voltage-clamp method shows 
some inherent deficiencies, which in some experimental conditions interfere with, or even 
prevent recording of the end-plate current. Therefore, the method was improved by attaching
 a “current pump” to the end of the feed-back 
loop. The aim of this work was to test the new
 method of the “current pump assisted” voltage
 clamp in the curarized sartorius m. of the frog. Qualitatively the results are the same as those
 obtained by the “plain” voltage-clamp. However, the “current pump-assisted” voltage-clamp is
 more stable and allows the use of a low-resistance current microelectrode. The set-up can be
 easily adapted for the classical method using
 two microelectrodes, as well as for microiontophoresis.