Fig. 9.

The slow AHP is associated with an increase in membrane conductance. A, Intracellular injection of sinusoidal current results in the generation of a prolonged AHP (current clamp). B, In hybrid current and voltage clamp, the injection of a similar series of sinusoidal current is associated with the generation of a prolonged outward current. C,The intracellular injection of hyperpolarizing voltage steps reveals that the outward current is associated with a 46% increase in membrane conductance. D, Apparent input resistance measured 10 sec after the end of sinusoidal injection in normal solution, expressed as a percentage of the resistance observed before the sinusoidal current injection. E, F, Change in apparent input resistance 10 sec after current injection varies with recordings conditions. The decrease is larger on average in low calcium-containing medium (E) than in normal solution (D). In low sodium (26 mm), there is an increase in apparent input resistance (F).