Figure 4.

Enhanced AMPH-induced Fos expression in both DA D1- and D2-receptor expressing MSNs of the NAc in mice with PV+ GABAergic interneurons silenced. (a) Fos immunofluorescence in the NAc of mice expressing either GFP or TeLC in PV+ interneurons of the NAc 2 h following administration of saline, 3 mg/kg AMPH, or the challenge dose of 3 mg/kg AMPH i.p. following the protocol shown in Figure 2d. Scale bar, 100 μm. (b) Quantification of the immunostaining from (a). n=9 mice/virus for AMPH and challenge groups, n=3 mice/virus for saline, *p<0.05 GFP vs TeLC within a treatment group. (c) Triple color fluorescence in situ hybridization for Fos, Drd1, and Drd2 in the NAc of mice 1 h following administration of the challenge dose of 3 mg/kg AMPH i.p. Nuclei (Nuc) are labeled in blue by Hoeschst. Colabeling of cells is indicated in the Fos panel as follows: 1, colocalizes with Drd1; 2, colocalizes with Drd2, N colocalizes with neither. Colocalization can be seen in the overlay panels to the right of Fos. Scale bar, 25 μm. (d) Quantification of the percent of Fos+ cells in the NAc that overlap Drd1 or Drd2 in mice expressing GFP or TeLC in PV+ GABAergic interneurons of the NAc. Percent was calculated as the number of Fos+ cells colabeled for Drd1 or Drd2 divided by the total number of Fos+ cells in the same section. n=5 mice/virus. (e) Colocalization of Fos in the NAc after repeated AMPH with Ppp1r1b, which encodes the MSN marker Darpp-32. Three cells highlighted by asterisks in the yellow box are shown in the enlargement of the merge at right, in which one (upper left) does not colocalize with Ppp1r1b. Scale bar, 50 μm.