Fig. 3.

Ba²⁺-Sensitive conductance-mediated changes in V_m and R_in stem from GIRK conductance in dorsal CA1 neurons. A and E: representative voltage responses with step current commands at RMP are shown. B and F: time courses of changes in V_m and R_in during successive 0.3 μM Tertiapin-Q and 50 μM Ba²⁺ application in dorsal (B) and ventral (F) CA1 pyramidal neurons. C and D: dorsal CA1 neurons showed a significantly depolarized V_m (C) and an increased R_in (D) following bath application of Tertiapin-Q (0.3 μM). Subsequent blockade of Ba²⁺-sensitive conductance showed no significant changes in V_m (C) and R_in (D) in dorsal CA1 neurons. G and H: ventral CA1 neurons showed no significant changes in V_m and R_in in the presence of Tertiapin-Q (0.3 μM). Further changes in V_m and R_in were not observed following blockade of Ba²⁺-sensitive conductance in ventral neurons. Blockade of Tertiapin-Q and Ba²⁺-sensitive conductance produced a significantly depolarized V_m and increased R_in compared with baseline in ventral neurons. I and J, left: representative voltage responses with step current commands at −73 mV. Dorsal CA1 neurons showed a significantly increased R_in (I) but not ventral CA1 neurons (J) at a common V_m (−73 mV) following successive Tertiapin-Q and Ba²⁺ application. K and L: representative V_m responses with depolarizing current steps (300 pA for 750 ms) at a common V_m (−73 mV). K: dorsal neurons showed significant increases in action-potential (AP) firing after either Tertiapin-Q or Tertiapin-Q + Ba²⁺ application but not ventral neurons (L). *P < 0.05.