Fig. 1: Basal forebrain (BF) neurons located in the nucleus accumbens shell (NAcs) and the ventral pallidum (VP) project to the LHb and express CB1R mRNA, GADs mRNA, or both.

A Retrograde tracer FG was delivered into the LHb. B FG-IR in the injection site (brown). C Low magnification of a NAc shell (d) and VP (e) coronal section showing detection of FG-immunoreactivity (FG-IR, blue), expression of CB1 mRNA (red), and expression of GADs mRNA (green). These areas in yellow boxes are shown at higher magnification in the sequence shown in (E), top and bottom, respectively. D Number of FG-IR cells detected in VP and NAcs, sorted by co-expression of CB1R mRNA and/or GADs mRNA. A total of 208 FG-IR VP neurons projecting to the LHb were detected, and of these 24 (13%) expressed only CB1R mRNA, 59 (28%) expressed only GADs mRNA, 80 (38%) co-expressed CB1R and GADs mRNA, and 45 (21%) lacked both CB1R and GADs mRNA. A total of 369 FG-IR NAcs neurons projecting to the LHb were detected, and of these 97 (26%) expressed only CB1 mRNA, 79 (21%) expressed only GADs mRNA, 67 (18%) co-expressed CB1R and GADs mRNA, and 126 (34%) lacked both CB1R and GADs mRNA. FG-IR cell counts were made between +1.92 and +0.72 mm from bregma (n = 3 rats, 8–9 sections per rat). E NAcs and VP areas corresponding to boxes (d, e) in panel (C) at higher magnification. FG-IR neurons expressing CB1R mRNA without GADs mRNA are indicated by single arrows, FG-IR neurons expressing GADs mRNA and CB1R mRNA are indicated by single arrow heads, and double arrow heads indicate FG-IR without GADs or CB1R mRNA in NAcs. A FG-IR neuron expressing GADs mRNAs, without CB1R mRNA in VP is indicated by double arrows. Abbreviations; aca, anterior commissure; LHb, lateral habenula; MHb, medial habenula; fr, fasciculus retroflexus.