Fig. 1.
Dorsal neurons show greater response to barium (Ba2+) compared with ventral Cornu Ammonis area 1 (CA1) neurons. A and E: representative voltage responses with step current commands at resting membrane potential (Vm; RMP). B and F: time courses of changes in Vm and input resistance (Rin) during successive Ba2+ (50 μM) and ZD7288 (10 μM) wash-in experiments in dorsal (B) and ventral (F) CA1 pyramidal neurons. C and D: dorsal CA1 pyramidal neurons showed a significantly depolarized Vm (C) and increased Rin (D) in the presence of Ba2+. Subsequent ZD7288 application resulted in a significantly hyperpolarized Vm (C) and an increased Rin (D). G and H: ventral CA1 pyramidal neurons showed no significant changes in Vm (G) and Rin (H) in the presence of Ba2+. Addition of ZD7288 led to a significantly hyperpolarized Vm (G) and an increased Rin (H). I and J, left: representative voltage responses with step current commands at −73 mV. Dorsal CA1 neurons showed a significantly increased Rin but not ventral CA1 neurons at a common Vm (−73 mV) in the presence of Ba2+. K and L: dorsal CA1 neurons showed a more hyperpolarized RMP (K) and a lowered Rin at RMP (L) compared with ventral CA1 neurons. There is no difference in Vm (K) and Rin (L) between dorsal and ventral neurons following successive Ba2+ and ZD7288 application. M and N: dorsal neurons showed significant changes in voltage-current (V-I) curve before and after 50 μM Ba2+ application (M) but not ventral neurons (N). O: the differences in V-I curves before and after 50 μM Ba2+ application are indicated. *P < 0.05; #P < 0.05 in dorsal vs. ventral groups. ΔVm, change in Vm; Iinj, injected current. Blue circles throughout figures represent mean number.