Figure 8. Cholinergic depolarization in layer II parasubicular neurons is mediated by an inhibition of a Ba²⁺-sensitive K⁺ conductance.

A. Mean group data show that Ba²⁺ (200 µM) induces a strong inward current in cells held at −60 mV, and that CCh (50 µM) fails to induce any additional inward current in the presence Ba²⁺ (*: p<0.05). B. Current traces in response to slow voltage ramps from −120 mV to −40 mV are shown for tests in the presence of TTX (0.5 µM) and ZD7288 (50 µM), after the addition of Ba²⁺ (200 µM), and after the addition of CCh (50 µM) (B₁). Current subtractions (B₂) show that Ba²⁺ induced an inward current consistent with suppression of an outward K⁺ current at voltages negative to E_K, and that subsequent application of CCh failed to elicit an additional current. The inward current induced by CCh in the presence of XE-991 (see Fig. 7) is therefore mediated by a Ba²⁺-sensitive K⁺ current.