Fig. 3: Photoactivation of VTA TH+ neurons induces dopamine release, whereas rtCPP retrieval induces dopamine, noradrenaline, and glutamate release in aIC.

a Diagram of virus infection, photoactivation of VTA TH+ neurons, and microdialysis guide cannula implantation into aIC. b Relative extracellular concentration of neurotransmitters compared with the baseline before, during, and after the photoactivation of VTA (blue bar) in eYFP (n = 4) and ChR2 (n = 4) mice. Horizontal blue bars indicate photoactivation of VTA. In vivo microdialysis (orange bar) revealed that extracellular concentration of dopamine (DA) increased during the VTA stimulation in ChR2 mice. For DA, Mann–Whitney test showed difference between eYFP vs. ChR2 during VTA stimulation U value = 0, P = 0.0286. Noradrenaline (NA), Glutamate (GLU), and gamma-aminobutyric acid (GABA) did not show statistically significant changes. c Diagram of virus infection, microdialysis guide cannula implantation into aIC and real-time conditioning place preference (rtCPP). d Relative extracellular concentration of neurotransmitters compared with the baseline before, during (Post-cond) and after the rtCPP retrieval in eYFP (n = 4) and ChR2 (n = 6) mice. In vivo microdialysis (orange bar) revealed increased extracellular concentrations of DA, NE, and GLU due to the context exposure during rtCPP retrieval in ChR2 mice. For GLU, Mann–Whitney test showed difference between eYFP vs. ChR2 during Post-cond U value = 1, P = 0.0190 and after rtCPP U value = 0, P = 0.0095. For NA, Man–Whitney test showed difference between eYFP vs. ChR2 during Post-cond U value = 0, P = 0.0095. For DA, Mann–Whitney test showed difference between eYFP vs. ChR2 during Post-cond U value = 0, P = 0.0095. All data are shown as mean ± SEM. *P < 0.05, **P < 0.001.