Characterization of immature and mature 5-hydroxytryptamine 3A receptor-expressing cells within the adult SVZ-RMS-OB system.

Neural stem cells in the subventricular zone (SVZ) generate progenitors which in turn give rise to neuroblasts. These neuroblasts then migrate along the rostral migratory stream (RMS) in chains and reach the olfactory bulb (OB), where they mature into local interneurons. Interneurons in the OB are heterogeneous, which are mainly located in granular cell layer (GCL), external plexiform layer (EPL) and glomerular layer (GL). In this study, we show that green fluorescent protein-expressing (GFP+) cells in the SVZ and RMS of the 5HT3aR-BAC(EGFP) transgenic mouse exclusively express transcription factor Sp8 which is expressed in lateral ganglionic embryonic eminence (LGE) and postnatal SVZ. These GFP+ neuroblasts of the 5HT3aR-BAC(EGFP) transgenic mouse migrate along the RMS to the OB where they differentiate into calretinin+ (CR+), parvabumin+ (PV+), vasoactive intestinal peptide+ (VIP+), somatostatin+ (Som+) and tyrosine hydroxylase+ (TH+), but not calbindin+ (CB+) interneurons. These GFP+ interneurons continuously express Sp8 in the OB. Furthermore, these results suggest that GFP-expressing cells are derived from LGE, and this transgenic mouse line will be a useful tool for studying the development and function of interneurons in both neocortex and OB.