The dendritic response to GABA in CA1 of the hippocampal slice.

Application of GABA in the dendritic region of pyramidal cells elicits a depolarization which, in fact, is the sum of a hyperpolarizing and a depolarizing process. At the reversal potential of the depolarizing response (-42 mV) the GABA-induced current fluctuations do not have a minimum. Consequently, a conductance change to more than one ion is involved. Cl- is in part responsible, Ca2+ is not because Mn2+ and Mg2+ do not change the response. Whether Na+ is involved is uncertain. Substitution with choline had no effect but choline may permeate through the membrane during the depolarizing response. Nipecotic acid inhibits a Na+-GABA uptake mechanism but does not change the dendritic response.