Figure 2.

In situ hybridization revealed no SERT mRNA expression in the MRN (A and B) and DRN (A and C) of SERT KO rats. Intra-raphe infusion of a viral vector encoding either of two shRNA sequences targeting SERT mRNA (shSERT1 or shSERT2) reduced the local expression of SERT mRNA (D). shSERT2 was more effective than shSERT1 in reducing local SERT expression. Eight weeks following intra-MRN injection of shSERT2, SERT expression levels in the MRN, but not DRN, were reduced (E, F and G). Eight weeks following intra-DRN injection of shSERT2, DRN, but not MRN, SERT expression levels were reduced to a similar extent (H, I and J). Both constitutive SERT KO and local SERT KD reduced the number of open arm entries on the EPM (K, L and M) without affecting locomotor activity (N, O and P) in cocaine-naïve rats. The increase in anxiety-related behavior in cocaine-naïve SERT KO rats (K) was accompanied by a decrease in CRF immunodensity in both the PVN (Q) and CeA (T). In contrast, the increase in anxiety-related behavior in cocaine naïve MRN shSERT rats (L) was accompanied by a decrease in CRF immunodensity in the PVN (R), but not the CeA (U), whereas the increase in anxiety-related behavior in cocaine-naïve DRN shSERT rats (M) was accompanied by a decrease in CRF immunodensity in the CeA (V), but not the PVN (S). All data are normalized to values obtained in SERT WT or shSCR control rats (see Supplementary Table S4 for absolute values of SERT expression and Supplementary Tables S5–S7 for absolute values of cocaine intake, EPM behavior and CRF levels). *Significant decrease (P<0.05) relative to SERT WT or shSCR, ^#significant difference (P<0.05) between shSERT2 and shSERT1, n.s: no difference relative to control. SERT WT (blue): n=13, SERT KO (green): n=10; MRN shSCR (blue): n=9, MRN shSERT2 (orange): n=9; DRN shSCR (blue): n=15, DRN shSERT2 (purple): n=15.