Fig. 1.

Fluorescence imaging of calcium transients induced in spine regions by low-frequency synaptic stimulation. Neurons in dissected E15 ciliary ganglia were filled with Oregon green-1–dextran via the postganglionic nerve root and then imaged with a multi-photon laser-scanning microscope at 18.5 msec/frame before, during, and after synaptic stimulation through the preganglionic nerve root.A–C, Single frames of a neuron taken 20 msec before, immediately after, and 1 sec after delivering a single synaptic stimulus. D–F, Averaged images of eight successive responses to 1 Hz stimulation taken 20 msec before, immediately after, and 800 msec after each stimulus. G, Labeling with rhodamine-conjugated α-Bgt for 10 min at the end of the experiment to identify α7-nAChR clusters defining spine mats. The same neuron is shown throughout. A single stimulus produces calcium transients in discrete regions along the perimeter. Averaging the responses intensifies the signal and shows that the calcium transients consistently correlate in location with spine mats defined by α7-nAChR clusters. A total of 20 neurons was examined in this manner and gave similar results. Arrow, A spine mat (on-spine);arrowhead, a region lacking detectable spines (off-spine). Scale bar, 10 μm.