Spine size of abGCs does not change after parturition. A, The time line of the experimental protocol in lactating mothers. In naive virgins, brains were fixed on the same neuronal day post-injection as in lactating mothers. B, Left, Projection image from a coronal slice of the OB populated with abGCs. Middle and Right, Higher resolution confocal images of the dendritic tree from the left image (consecutive magnifications are marked with a white box). Scale bars: left, 100 μm; middle, 20 μm; right, 10 μm. GL, glomerular layer; EPL, external plexiform layer; GCL, granule cell layer. C, Top, Projection image of one dendritic segment analyzed for spine head sizes. Four representative spine heads are marked with red arrowheads and their size values are indicated by a number. Larger numbers indicate larger spine heads. Spine size values are in AU. Scale bar: 5 μm. Bottom, An example of one imaged spine taken from the above dendritic segment (dashed box). Color intensity indicates fluorescence intensity. The regions marked for analysis are: head (left), adjacent background (middle), and adjacent dendritic shaft (right; see Materials and Methods, Data analysis, for details). D, Spine size distributions of abGC spines in naive virgins (white bars; n = 1869 spines from 23 cells in 6 mice) and lactating mothers (gray bars; n = 1947 spines from 26 cells in 7 mice).