Q-PCR revealed that the expression levels of Bdnf, Vegf, and Igf1 mRNA were significantly increased by continuous IMI treatment, but were not affected by CUMS ( Figures S5B, S5D, and S5H). Interestingly, the mRNA levels of Gdnf and Nt-3 in the STR and HP, respectively, were significantly decreased by CUMS, and these effects were reversed by continuous IMI treatment ( Figures S5A and S5E). In addition, the mRNA expression level of Gdnf in stressed BALB mice

was significantly decreased in both the dorsal STR (dSTR) and the ventral STR (vSTR) ( Figure 1A). On the contrary, the mRNA expression level learn more of Gdnf in stressed B6 mice was significantly increased in the vSTR but not in the dSTR ( Figure 1B). These changes in GDNF expression were confirmed at the protein level using CH5424802 order an ELISA assay ( Figure 1C). These results suggest that the transcriptional regulation of Gdnf in the vSTR is differentially regulated in the two mouse

strains and may contribute to the observed behavioral responses to CUMS. We next investigated whether a correlation exists between Gdnf expression in the vSTR and behavioral performances in mice. We found that GDNF protein levels in the vSTR of nonstressed BALB and B6 mice were significantly correlated with social interaction time ( Figure 1D) and sucrose preferences ( Figure 1E), but not with immobility times in the forced only swim test ( Figure 1F) or the latency to feed in the novelty-suppressed feeding test ( Figure 1G). These data suggest an important role for GDNF in the vSTR for determining certain types of depression-like behaviors. To directly investigate the role of GDNF in depression-like behaviors, GDNF was overexpressed in the NAc of mice using the polyethylenimine (PEI) gene delivery system. The experimental design is shown in Figure S1B. The successful transduction of EGFP (Figure 1H) and GDNF (Figure 1I) into the NAc of mice using this system was confirmed. We first

assessed social interaction time and sucrose preference for nonstressed B6 mice 2 weeks after the injections of PEI/Gdnf or PEI/Egfp complexes. We found that GDNF overexpression increased the social interaction time ( Figure 1J), but not the sucrose preference ( Figure 1K). We next investigated the effect of GDNF overexpression in stressful conditions. BALB mice were subjected to 4 weeks of CUMS and injected bilaterally into the NAc with either PEI/Gdnf or PEI/Egfp complexes on day 14 of the CUMS session. After the CUMS session, we performed behavioral assays. We found that the social interaction time ( Figure 1J) and sucrose preference ( Figure 1K) of the stressed BALB mice that received PEI/Gdnf complexes were significantly greater than those of the mice receiving PEI/Egfp complexes. These results suggest a crucial role for GDNF in social interactions and sucrose preference.