Figure 5.
The coupling between Na+ and Ca2+ dynamics leads to prolonged Ca2+ transients and labeling of active synapses. (A) The relationship between [Na+]i and stable-state [Ca2+]i calculated using the parameters used for the mitral cell dendritic tuft (solid line) or a 10-fold reduction (dotted line) or increase (dashed line) in the Na+-Ca2+ exchanger density. (B) The stable-state [Ca2+]i (dashed black line) and actual [Ca2+]i (blue line) in the dendritic tuft of the mitral cell model during and after a 30 Hz spike train (red bar). (C) Indicating the distal dendritic site (arrow) and “hot zone” site (arrowhead) used to test the effect of synaptic stimulation on [Ca2+]i dynamics in the pyramidal cell model. (D) The effect of repeated synaptic stimulation (black triangles) in the distal site on local [Ca2+]i with (thick green line) or without (light green line) concurrent back-propagating Ca2+ spikes (red triangles). The effect of the calcium spikes alone is indicated by a magenta line, and the stable-state [Ca2+]i by a black dotted line. (E) Similar to (C), except for stimulation in the Ca2+ “hot zone” (the site indicated by an arrowhead in C). (F) The effect of repeated parallel fiber stimulation (black triangles) on local [Ca2+]i with (thick red line) or without (light red line) concurrent climbing fiber stimulation (red triangles). The parallel fiber stimulation site is indicated by an arrow on the dendritic tree (right) and the climbing fiber input sites by yellow segments. The effect of the complex spikes alone is indicated by an orange line, and the stable-state [Ca2+]i by a black dotted one.