Fig. 12.

The absence of detectable electrotonic coupling in paired recordings from SCN neurons. (A) Cell 1 (top of panel) was injected with negative current pulses of various intensities (1–4) and the voltage responses recorded from cell 2 (i.e., the four traces at the bottom of the panel; 1–4) are shown as single sweeps corresponding to the four negative current pulses above. (B) Cell 1 was injected with negative current pulses of long duration (1 nA, 600 msec), but no post-junctional voltage deflection was recorded in cell 2 (i.e., lack of evidence for electrotonic coupling between this pair). However, spontaneous spikelets were recorded from cell 2, presumably arising from coupling between cell 2 and a third cell.