Characterization Of Immature And Mature5-hydroxytryptamine3A Receptor-expressing Cells Within The Adult SVZ-RMS-OB System

Adult neurogenesis occurs on two pathways in mammal brains, of which one is the subventricular zone (SVZ)-rostral migratory stream (RMS)-olfactory bulb (OB) system. Neural stem cells populating the SVZ generate progenitors which give rise to neuroblasts. These neuroblasts then migrate along the RMS in chains and reach OB, where they mature into local interneurons and integtrate into the functional circuit. Interneurons in the OB are heterogeneous, which mainly locate in the granular cell layer (GCL), external plexiform layer (EPL), and glomerular layer (GL). Transgenic mice with specific cell type(s) reported by green fluorescent protein (GFP) have become a powerful tool for morphological and functional studies of neurons in the CNS. In the present study, we report a5-hydroxytryptamine receptor3A (5-HT3AR) transgenic mouse line (5-HT3aR-BACEGFP) in which expression of5-HT3AR was observed in immature and mature neurons in the SVZ-RMS-OB system. Majority of neuroblasts, but not neural stem cells and progenitors, in the SVZ express5-HT3AR (5-HT3AR+). And they also exclusively express transcription factor Sp8which is expressed in embryonic lateral ganglionic eminence (LGE) and postnatal SVZ, and regulates the production of OB interneurons. These5-HT3AR-expressing neuroblasts migrate along the RMS to the OB where they differentiate into calretinin+(CR+), parvalbumin+(PV+), vasoactive intestinal peptide+(VIP+), somatostatin+(Som+) and tyrosine hydroxylase+(TH+), but not calbindin+(CB+) interneurons, and continuously express Sp8. Furthermore, these results suggest that5-HT3AR-expressing cells are derived from LGE, and this transgenic mouse line will be a useful tool for the study of interneuron development and function in both neocortex and OB.