Pharmacogenetic inhibition of ventral tegmental area (VTA)/substantia nigra compacta (SNc) dopaminergic (DAergic) neurons in tyrosine hydroxylase (TH)-Cre mice.

Schematic representation of Cre-dependent adeno-associated virus (AAV) vectors expressing hM3Dq/hM4Di-mCherry under the control of human synapsin (hSyn) promoter. WPRE, woodchuck hepatitis virus post-transcriptional regulatory element; CNO, clozapine-N-oxide; IP, intraperitoneal. (B) Microinjection of AAV-DIO-hM4Di-mCherry into the VTA induced hM4Di expression (red). ml, medial lemniscus; SNc, substantia nigra, compacta; SNr, substantia nigra, reticular part. (C) Representative photomicrographs of the VTA depicting mCherry expression (red), TH (green), and 4,6-diamidino-2-phenylindole (DAPI, blue) immunoreactivity and merge images (yellow) from a TH-Cre mouse microinjected with Cre-dependent AAV vectors containing hM4Di. (D) Statistics of the coexpression of TH and mCherry immunofluorescence of VTA neurons (n = 3, per group). (E) Drawings of superimposed AAV-injected area in the VTA (left, n = 8) and SNc (right, n = 8) of TH-Cre mice with different colors. (F, H) Representative photomicrographs of mCherry expression after microinjection of AAVs containing hM4Di into the VTA (F) and SNc (H). (G, I) CNO (G, I; top) and saline (G, I; bottom) did not induce c-Fos expression in hM4Di-expressing DAergic neurons in VTA (G) or SNc (I). (J) In TH-Cre mice, the firing property of a recorded VTA hM4Di/mCherry-positive DAergic neuron with hyperpolarization-activated cation current (Ih) (top) and CNO perfusion inhibited its firing rate (bottom). Underlying data can be found in S1 Data.