Fig. 5.

Small hyperpolarizing current injections in the dendrites do not reveal a global shunt after a train of action potentials. A, Single trace response (top) showing the effect of a train of 33 action potentials in 1 sec on the response to a small hyperpolarizing current pulse (bottom; hyperpolarizing current injections are 10 pA and depolarizing current injection is 400 pA). Apical dendritic recording is 168 μm from the soma. B, Average of eight responses like the one in A. C, Enlarged view of the average control hyperpolarization before the train of action potentials. D, Enlarged view of the average test hyperpolarization after the train of action potentials. The afterhyperpolarization measured in the absence of a test pulse was subtracted from the response with the test pulse.