Figure 3. Intermittent weak electronic coupling between s.o. interneurones.

A, the first trace (from top to bottom) represents a single sweep recorded from the current-injected interneurone. The second trace is an averaged sweep of 20 consecutive sweeps from the other coupled interneurone. Electrotonic coupling is clearly seen in this sweep. Below are shown individual sweeps from the coupled interneurone. Note that coupled responses to current injections into the other cell, into which the current pulses are injected, are partially or completely absent from some of the individual traces. B, intermittent electrotonic coupling remains when chemical neurotransmission is blocked by perfusing the hippocampus with ACSF containing CNQX (20 μm), AP5 (25 μm), and bicuculline (20 μm). The top trace represents the averaged sweep of 16 consecutive sweeps from the current-injected cell. The second trace is the average of 16 sweeps from the other coupled neurone, showing electrotonic coupling between the two cells. The lower traces are individual sweeps from this cell. The electrotonic coupling is not obvious in some sweeps. C, the hippocampus was exposed to ACSF without added Ca²⁺, again to block chemical synaptic transmission. The top trace is a sweep from the current injected cell. The second trace is the average of 16 sweeps from the electrotonically coupled cell. The remaining traces are individual sweeps from the electrotonically coupled cell, again showing that this electrotonic coupling is intermittent.