Figure 3. Global versus Local Dendritic Ca²⁺ Signals.

(A) In situ Ca²⁺ imaging of MN5 with targeted expression of GCaMP6s reveals global Ca²⁺ signals during a train of action potentials as evoked by somatic ramp current injection. Upper image is at rest and lower image during a train of action potentials as induced by somatic ramp current injection (original images overlaid as false color code for gray values from 70 to 240). Eight regions of interest (ROIs) for ΔF/F measurement are depicted by numbered ovals.

(B) Simultaneous somatic current clamp (upper trace) and Ca²⁺ imaging recordings from all eight ROIs before, during, and after a train of action potentials reveals global increases in ΔF/F. Note different scale for ROIs 4 and 5 (soma and primary neurite), which displayed the largest amplitude signals upon firing.

(C) In situ Ca²⁺ imaging of the same MN5 with identical ROIs as in (A) at rest (upper image) and during a brief (5 ms) puff of nicotine (10⁻⁵ M) onto a distal dendrite (lower image).

(D) Simultaneous somatic current clamp (upper trace) and Ca²⁺ imaging recordings from all eight ROIs before, during, and after three consecutive nicotine puffs to ROI1. Nicotinic AChR activation in ROI1 caused locally restricted dendritic Ca²⁺ signals.

See also original data movies for global (Movie S1) and local (Movie S2) dendritic signals as well as Figure S4 and Movies S3 and S4 for local Ca²⁺ signals at different dendritic sites.