Figure 2. VTA-DA and VTA-GABA Neurons Receive Synaptic Inputs from Diverse Cell Types.

(A) Coronal schematic showing the paraventricular hypothalamus (PVH, blue) where inputs to VTA-DA and -GABA neurons were examined for expression of the mRNAs encoding either oxytocin (B₁, B₃) or arginine vasopressin (AVP; B₂, B₄) precursors.

(B) Overlap of in situ hybridization (ISH) signals (red) with GFP from RVdG (green) was observed for inputs to both VTA-DA (B₁-B₂) and VTA-GABA (B₃-B₄) neurons. Arrowheads indicate cells co-labeled with ISH probe and GFP.

(C) Quantification of percentage of total rabies-labeled inputs in the PVH that co-stained with ISH probe. Both oxytocin+ (p<0.001, t-test) and AVP+ (p=0.02) neurons showed a preference for sending input to VTA-GABA neurons. n=6 (mice) for both probes in DAT-Cre, and n=5 for both probes in GAD2-Cre.

(D–F) ISH in the lateral hypothalamus (LH) for genes encoding orexin (hypocretin) or neurotensin (NT), analogous to panels A–C. (F) Both orexin neurons (p=0.0143) and NT neurons (p=0.03) showed a preference for VTA-DA neurons. n=4 for all.

(G–I) ISH in the dorsal raphe (DR) for genes encoding Tph2, GAD1/2, VGluT1/2/3, and TH, in DAT-Cre mice. No TH⁺/GFP⁺ neurons were observed. (I) Serotonin (p=0.27), GABA (p=0.97), and glutamate (p=0.84) neurons did not show a preference for VTA-DA or VTA-GABA neurons. n=4 for all. The combined fraction exceeded 100% because a large fraction of neurons were both vGluT3⁺ and Tph2⁺.

All statistics were t-tests. p-values were obtained with Holm-Sidak correction for multiple comparisons where applicable. Scale, 100 μm.