Letrozole and reduce the number of dendritic spines. (a) Representative 3D reconstructions of dendritic segments from sister cultures that were treated with either control, (1 μM), and letrozole (1 μM) or + letrozole (1 μM) for 24 or 72 hours. Scale bar, 2 μm. (b) Quantification of the spine subtype densities following treatments. There is a significant decrease in the total dendritic spine densities for , letrozole, and + letrozole-treated cultures compared to control after 24 hours. When spine subtypes are examined, there are significant differences between control and treated cultures in mushroom and thin-type spines while spine density for stubby spines is only significantly different between letrozole and + letrozole compared to control and between and letrozole. Control, n = total dendritic segment lengths of 441 μm from 10 cells in 4 cultures; ,  μm of dendrite from 11 cells in 4 cultures; letrozole,  μm of dendrite from 9 cells in 4 cultures; + letrozole,  μm of dendrite from 10 cells in 4 cultures. There is a significant decrease in the total dendritic spine densities compared to control cultures after 72 hours as well. In total spine density, cultures treated with either letrozole or + letrozole had lower spine counts compared to cultures treated with alone. For mushroom and thin-type spines, cultures treated with both and letrozole had significantly lower spine densities compared to alone while stubby spine density was lower for letrozole-treated compared to alone. Control,  μm of dendrite from 12 cells in 4 cultures; ,  μm of dendrite from 10 cells in 4 cultures; letrozole,  μm of dendrite from 11 cells in 4 cultures; + letrozole,  μm of dendrite from 9 cells in 4 cultures. Only cultures treated with + letrozole had significant decrease in total spine densities between 24 and 72 hours of treatment. This difference is contributed by significant decrease in spine density in both mushroom and thin type spines.