Figure 2.

Parvalbumin-expressing interneurons are more concentrated in the dorsal versus the ventral striatum in male, but not female mice. (A) Representative whole striatum reconstruction of high-resolution microscope images of PV-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 PV-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 PV+ interneurons in the male CPu. (D) Higher resolution image of selected region from (B) showing PV+ interneurons in the female CPu. (E) Quantification of the density of PV+ interneurons per mm² over the whole mouse striatum using stereological methods shows similar densities of PV+ neurons between sexes (Two-tailed t-test, t[36] = 0.595; p = 0.56). (F) Quantification of the density of PV+ interneurons divided over the CPu and NAcc sub-regions of the striatum reveals a significant effect of subregion (Repeated Measures ANOVA, F(1, 29) = 57.06, p < 0.001) and a significant interaction of sex and subregion [F(1, 29) = 7.745, p = 0.009]. Males showed significantly higher PV+ interneuron density in the CPu compared to the NAcc (****Fisher’s LSD: p < 0.001) while females showed a similar, but less robust gradient (**p = 0.001). PV+ interneurons in the CPu were significantly denser in males than in females (*p = 0.011), but there were no differences in density in the NAcc (p = 0.97). (G) Alternate representation of data from (F) showing density gradients of PV+ interneurons from the CPu to the NAcc. Both males and females showed a dorsal to ventral gradient of PV interneurons, however this was significantly higher in males. Scalebars equal 20 μm.