Figure 1.

Specific Deletion of CB1 in Different Neuronal Subpopulations in Conditional CB1 Mutant Mice as Revealed by In Situ Hybridization with a Specific Riboprobe for CB1 mRNA

Micrographs showing CB1 mRNA expression in the brain of CB1^f/f (wt, [A]–[D]), CaMK-CB1^−/− (E–H), Glu-CB1^−/− (I–L), and GABA-CB1^−/− mice (M–P). Sections were stained throughout the brain and micrographs were taken at the level of caudate putamen (A, E, I, and M), dorsal hippocampus (B, F, J, and N) and cerebellum (C, G, K, and O).

(D, H, L, and P) Detailed enlargements of the dorsal hippocampus of (B), (F), (J), and (N), respectively. In all three mutant lines, deletion of CB1 is mainly restricted to the forebrain, with little or no alterations in the hindbrain (C, G, K, and O). In CaMK-CB1^−/− mice, CB1 mRNA is absent from all principal neurons and expressed only in GABAergic interneurons (intense scattered dots; E, F, and H). In Glu-CB1^−/− mice, CB1 mRNA is absent in the majority of cortical glutamatergic neurons (I, J, and L). In GABA-CB1^−/− mice, CB1 mRNA is absent in all GABAergic neurons and it is expressed only in non-GABAergic cells (low uniform gray staining; M, N, and P).