Fig 2: VTA injections of AAV9_Cre at lower titers do not alter behavioral or histological phenotypes. (A) Scheme visualizing bilateral injection of AAV9_Cre (1010 GC/mL) mixed with AAV9_DIO_GFP (2.99 × 1012 GC/mL; mixture hereafter simply denoted as Cre) and control AAV9_GFP (3.0 × 1012 GC/mL) into the VTA of adult WT C57BL/6J mice. (B,C) Distance traveled and center time spent in the open field task does not differ between Cre- and AAV9_GFP control-injected mice (n = 11/group; (B) two-way ANOVA, F(5,100) = 0.7684, p = 0.5747 and genotype: p = 0.5909; (C) mixed effects model, F(5,96) = 1.866, p = 0.1074 and genotype: p = 0.4474). (D) Anxiety assessed in the elevated plus maze is unaffected in Cre- and control-injected mice (n = 11/group; two-way ANOVA, F(1,20) = 0.00036, p = 0.9851 and genotype: p = 0.6528). (E) Spontaneous alternation measured in a Y-maze is slightly decreased in Cre- compared to control-injected mice (ctrl n = 7, Cre n = 8; unpaired t-test, p = 0.0442 *). (F) Sensorimotor gating is largely unaffected (ctrl n = 7, Cre n = 8; mixed effects model, F(2.184, 26.93) = 43.11, genotype: p = 0.5549, 66dB p = 0.0243 * (exclusion of two Cre values (~-30%) at 66 dB in outlier test, otherwise data would be non-significant). (G) Immunohistochemistry revealed normal histology in Cre-injected mice. (H,I) DAT and TH expression are comparable between Cre- and control-injected mice. Scale bars 500 µm.

Fig 3: The stimulant effect of D2R-DAT disruption is due to the rise of extracellular dopamine level in SD rats. a Schematic illustration and cresyl violet staining confirmation of cannula placement into both the lateral ventricle and nucleus accumbens core. The grey bars represent the cannula, whereas the black bar represents the 2-mm probe membrane. b Time-course raw traces of high performance liquid chromatography before and after the administration of TAT-DATNT was illustrated. The retention time of dopamine was determined to be at 5.08 min. c TAT-DATNT (40 nmol, i.c.v.) started to increase the extracellular dopamine level half an hour after its administration and such effect remained significant approximately for 2 hours (n = 5–6). The dotted line represented the time of intra-cranial injection. All data were presented as percent dopamine to baseline (%) ± SEM. *p < 0.05, **p < 0.01 and ***p < 0.001

Fig 4: RVG‐nDMC increases TH expression and DA synthesis in PD mice. A–C) Representative blots and quantification showing TH and DAT expression levels in the SN of Control, MPTP, and MPTP + RVG‐nDMC groups. n = 6 per group. D) Ultrastructural analysis of synaptic vesicles in the SN of the three groups. Scale bars, 500 nm. Black arrows show the morphological synaptic vesicles. E) Quantification of synaptic vesicles in the SN of the three groups. n = 10 per group. F) Typical HPLC chromatograms of DA, DOPAC, 5‐HT, and 5‐HIAA. G–J) The levels of DA, DOPAC, 5‐HT, and 5‐HIAA were assessed by HPLC‐MS/MS analysis. n = 4 per group. K–M) Representative blots and quantification showing Synapsin, Syntaxin, Synaptotagmin, and PSD‐95 expression levels in the SN of the three groups. n = 6 per group. Results are expressed as the mean ± SEM. ** p < 0.01 vs Control. ## p < 0.01, # p < 0.05 vs MPTP group. Statistical significance was determined by one‐way ANOVA and Tukey tests for post‐hoc comparisons.

Fig 5: Identification of cocaine binding proteins. (A) Western blot of DAT overexpressed in HEK 293 cells following IP with anti-cocaine antibody. Input of DAT and actin from the same sample used in IP serve as loading controls. L104V-F105C-A109V triple mutant DAT is insensitive to cocaine. (B) Schematic diagram of the protocol used to identify cocaine binding proteins. (C and D) MS/MS spectra of the peptides used to identify the brain acid soluble protein 1 (BASP1) in anti-cocaine immunoprecipitates.