Figure 3.

Somatostatin-expressing interneurons are denser in the ventral striatum in both male and female mice. (A) Representative whole striatum reconstruction of high-resolution microscope images of SOM-expressing interneurons in a male mouse brain, with dashed lines indicating counting regions for CPu and NAcc. (B) Representative whole striatum reconstruction of high-resolution microscope images of SOM-expressing interneurons in a female mouse brain, with dashed lines indicating counting regions for CPu and NAcc. (C) Higher resolution image of selected region from (A) showing SOM+ interneurons in the male CPu. (D) Higher resolution image of selected region from (B) showing SOM+ interneurons in the female CPu. (E) Quantification of the density of SOM+ interneurons per mm² over the whole mouse striatum using stereological methods, showing similar densities of SOM+ neurons between sexes (Two-tailed t-test, t[27] = 0.515, p = 0.61). (F) Quantification of the density of SOM+ interneurons divided over the CPu and NAcc sub-regions of the striatum reveals a significant effect of subregion (Repeated Measures ANOVA, F(1, 23) = 27.45, p < 0.001) and no effect of sex [F(1, 23) = 0.9600, p = 0.337] or interaction [F(1, 23) = 0.01914, p = 0.891]. Both males and females showed significantly higher SOM+ interneuron density in the NAcc compared to the CPu (**Fisher’s LSD: p = 0.001 for both) with no sex differences in density for either the CPu (p = 0.404) or the NAcc (p = 0.346). (G) Alternate representation of the data from (F) showing a significant density gradient from the NAcc to the CPu in both males and females of equal significance (Fisher’s LSD: ***p = 0.0003, **p = 0.009). Scalebars equal 20 μm.