Figure 6.

Time-lapse in vivo two-photon imaging reveals that OVX reduces spine density by both increasing the rate of spine loss and decreasing the rate of spine addition. A, Left, Time line for experiments using time-lapse two-photon imaging of apical dendrites projected from layer 5 pyramidal neurons in layer 1 region of somatosensory cortex. Right, An isoflurane-anesthetized, head-fixed mouse with chronically implanted cranial window under the two-photon microscope. B, Representative images showing a segment of apical dendrite before (d4) and after (d20) sham or OVX surgery. The red arrowheads mark the spines that will later be lost, and the yellow ones mark the newly gained spines. The plots summarize the spine density changes before and after sham (67 dendritic segments from 4 mice) and OVX (59 dendritic segments from 7 mice) surgeries. C, The bar graphs summarize the gained and lost rate, as well as TOR of spines, all calculated by comparing to the previous time point. The line plot shows the survival rate of all spines present on d3. The paired two-tailed Student's t test was used for before/after comparisons, the unpaired two-tailed Student's t test for the sham/OVX group comparisons, and repeat measures two-way ANOVA with Bonferroni's post hoc test for survival rate comparison. *p < 0.05, ***p < 0.001.