Figure 3.

Electrically coupled spikelets and bAP-evoked Ca²⁺ transients in the apical tuft of mitral cells are not decreased with somatic hyperpolarization. A, Somatic APs recorded from the presynaptic mitral cell (M₁) narrow at V_hyper (representative average traces on the left; black, V_rest; gray, V_hyper). AP traces are overlaid by the AP generation threshold (dashed line). M₂, postsynaptically recorded spikelets were aligned with the peak of the presynaptic AP and overlaid by the spikelet generation threshold (representative average traces on the right; black, V_rest; gray, V_hyper). Arrows indicate AP and spikelet initiation. Summary charts show AP width at half amplitude (bottom left; n = 8) and spikelet amplitude and width at half amplitude (bottom right). Black dots connected with thick black lines represent the means of eight individual experiments. ***p < 0.001. B₁, Representative traces of a pair of bAPs (top) and Ca²⁺ transients (20 Hz, bottom) were measured in the apical tuft at V_rest (black) and V_hyper (gray). Sets of five sweeps at V_rest were alternated with sets of five sweeps at V_hyper. Inset, bAP-evoked Ca²⁺ transients are adjusted according to the basal [Ca²⁺]. B₂, Summary chart shows Ca²⁺ transient amplitudes (Amp1, Amp2) at V_rest and V_hyper in the tuft and apical dendrite (Ad). Ca²⁺ transient amplitudes in the tuft (n = 7) are increased with hyperpolarization, although there is no significant change in the apical dendrite (n = 5). *p < 0.05.