Cell type-specific loss of BDNF signaling mimics optogenetic control of cocaine reward - PubMed (original) (raw)

Fig 1. Effect of selective deletion of TrkB from D1+ or D2+ MSNs on behavioral effects of cocaine, c-Fos induction, and neuronal excitability

(A) TrkB mRNA is expressed in D1+ and D2+ MSNs FACS-purified from D1-GFP and D2-GFP transgenic mice, but is significantly enriched in D2+ MSNs (n = 4 per group); Student’s t-test, p < 0.05). (B) D1-Cre–flTrkB (n = 9) mice displayed enhanced cocaine conditioned place preference (CPP) relative to littermate controls (n = 10), whereas (C) D2-Cre–flTrkB mice (n = 14) exhibited decreased cocaine CPP compared to littermate controls (n = 16) (cocaine dose: 7.5 mg/kg ip; Student’s t-test, **p < 0.01, *p < 0.05). (D,E) D1-Cre–flTrkB and D2-Cre–flTrkB mice and littermate controls were treated with saline on day 0 and with cocaine (10 mg/kg) on days 1–7 and locomotor activity was assessed over a 30-min time period. (D) D1-Cre–flTrkB mice (n = 6) displayed enhanced cocaine-induced locomotor activity after repeated cocaine administration compared to littermate controls (n = 7) (Repeated Measures Two-Way ANOVA, genotype effect: F(1,11) = 6.20, p < 0.05; day effect: F(6,66) = 5.50, p < 0.01), while (E) D2-Cre–flTrkB mice (n = 10) showed decreased locomotor activity to acute and repeated cocaine relative to controls (n = 14) (Repeated Measures Two-Way ANOVA, genotype effect: F(1,22) = 9.98, p < 0.01; day effect: F(6,132)= 4.00, p < 0.01). Post-hoc analysis reveals significant differences on specific cocaine days (Student’s t-test, **p <0.01, *p < 0.05). Data represented as mean ± SEM. (F–I) c-Fos induction was examined 90 min after acute cocaine (20 mg/kg) by double immuno-labeling of c-Fos (green) and Cre (red) in the NAc. (F,H) D1-Cre–flTrkB mice exhibited a significant decrease in double-labeled c-Fos (green) and Cre (red) neurons in the NAc after cocaine exposure compared to D1-Cre control mice and this down-regulation is specific to the NAc shell. (G,I) In contrast, D2-Cre–flTrkB mice, relative to D2-Cre controls, displayed an increase in double-labeled c-Fos and Cre neurons in the NAc, an effect also specific to the NAc shell (n = 4 per group, Student’s t-test, **p < 0.01, *p < 0.05). Images displayed are from the NAc shell. Arrows represent neurons double labeled with c-Fos and Cre. Arrowheads represent c-Fos neurons that are not Cre positive. Scale bars, 20 µm. Data represented as mean ± SEM. (J) Sample traces obtained by 200 pA current injection (holding potential at −80 mV) in NAc shell MSNs in D1-Cre-flTrkB, D2-Cre-flTrkB, and their control mice injected with DIO-AAV-EYFP into the NAc for visualization of D1+ or D2+ MSNs. (K,L) D2+ MSNs in D2-Cre-flTrkB NAc (n=3 animals), but not from D1+ MSNs in D1-Cre-flTrkB NAc (n=4), display increased cell excitability following incremental steps in current injections (100, 150, and 200 pA) compared to respective controls, D2-Cre (n=5) and D1-Cre (n=8). Two-way ANOVA, F(1,7) = 13.23, p = 0.002 (for D2+ MSNs), F(1,11) = 4.04, p = 0.054 (for D1+ MSNs). Post hoc analysis reveals significant effects for 100 and 150 pA currents in D2+ MSNs, Student’s t-test, *p<0.05.