Figure 7.

Gap junctions prevent postsynaptic firing by inducing V_m hyperpolarization at near-threshold levels. (A) Example of a GJ-only connected pair in which FSI₁ displayed an array of subthreshold spikelets in response to a train of AP occurring in FSI₂ during DC injection in both cells (380 and 405 pA, respectively, 20 s). The average V_m value of FSI₁ during the spikelet barrage was measured throughout the duration of FSI₂ burst (indicated by the white bar) and compared to the average V_m value before the burst onset (black bar). Right, summary of average V_m values measured in FSI₁ before (left column) and during (right column) barrages of 4–8 spikelets occurring in response to AP burst in FSI₂. Mean V_m ± s.e.m. values were significantly different in the two conditions (n = 22 pairs, ^*p < 0.05, paired t-test). (B) Same experiment as in (A), but with non-connected FSIs. Mean V_m ± s.e.m. in FSI₁ did not change significantly during a burst in FSI₂ (n = 10 pairs, p > 0.05, paired t-test). Transient changes in V_m corresponding to AP firing were excluded from measurements.