CB1 mRNA Is Expressed in Glutamatergic Cortical Neurons and in Glutamatergic Mossy Cells of the Dentate Gyrus, as Revealed by Double In Situ Hybridization Experiments in Wild-Type C57BL/6N Mice and Conditional Mutants
(A–D) Micrographs showing coexpression of CB1 mRNA (red staining) with VGluT1 mRNA (silver grains) in the CA3 region of hippocampus (A), basolateral amygdala (B), entorhinal cortex (C), and hilus of dentate gyrus (D) of wild-type C57BL/6N adult mice. Filled arrows, GABAergic interneurons, expressing CB1, but not VGluT1. Open arrows, glutamatergic neurons, coexpressing CB1 and VGluT1.
(E–H) Micrographs showing coexpression of CB1 mRNA (red staining) with GAD65 mRNA (silver grains), in the hilus of dentate gyrus in CB1f/f (E), GABA-CB1−/− (F), CaMK-CB1−/− (G), and Glu-CB1−/− mice (H). Filled arrowheads, GABAergic interneurons, coexpressing CB1 and GAD65 mRNAs. Open arrowheads, presumable glutamatergic neurons, not coexpressing CB1 and GAD65 mRNAs.
Note that high CB1-expressing cells do not coexpress VGluT1 mRNA (A–D), but do coexpress GAD65 mRNA (E–H), showing that they are GABAergic interneurons. Conversely, low CB1-expressing cells coexpress VGluT1 mRNA (A–D), but do not contain GAD65 mRNA (E–H), showing that they are glutamatergic neurons. In particular, glutamatergic hilar mossy cells contain CB1 mRNA in wild-type (D), CB1f/f mice (E), and GABA-CB1−/− (F), but not in CaMK-CB1−/− (G) and Glu-CB1−/− mice (H). Blue staining, toluidine blue nuclear counterstaining. GC, granule cells of dentate gyrus. Pyr, CA3 pyramidal neurons. Bar, 25 μm.