Figure 2. The presynaptic I_h is caesium sensitive and barium insensitive.

A hyperpolarizing voltage step from -70 to -120 mV lasting 3 s was applied to a presynaptic terminal every 30 s. The amplitude of the inward current measured at the end of the voltage step is plotted against time. Example traces are shown on the right. Addition of BaCl₂ (2 mm) to the ACSF had no effect on the current amplitude or kinetics, whereas CsCl (2 mm) reversibly blocked the hyperpolarization-activated current.