title: Second-order input to the medial amygdala from olfactory sensory neurons expressing the transduction channel TRPM5.
abstract: Recent anatomical tracing experiments in rodents have established that a subset of mitral cells in the main olfactory bulb (MOB) projects directly to the medial amygdala (MeA), traditionally considered a target of the accessory olfactory bulb. Neurons that project from the MOB to the MeA also show activation in response to conspecific (opposite sex) volatile urine exposure, establishing a direct role of the MOB in semiochemical processing. In addition, olfactory sensory neurons (OSNs) that express the transient receptor potential M5 (TRPM5) channel innervate a subset of glomeruli that respond to putative semiochemical stimuli. In this study, we examined whether the subset of glomeruli targeted by TRPM5-expressing OSNs is innervated by the population of mitral cells that projects to the MeA. We injected the retrograde tracer cholera toxin B (CTB) into the MeA of mice in which the TRPM5 promoter drives green fluorescent protein (GFP). We found overlapping clusters of CTB-labeled mitral cell dendritic branches (CTB(+) ) in TRPM5-GFP(+) glomeruli at significantly greater frequency than expected by chance. Despite the significant degree of colocalization, some amygdalopetal mitral cells extended dendrites to non-TRPM5-GFP glomeruli and vice versa, suggesting that, although significant overlapping glomerular innervation is observed between these two features, it is not absolute.
authors: Rocky Mountain Taste and Smell Center, Department of Cell and Developmental Biology, Aurora, Colorado 80045, USA. john.a.thompson@ucdenver.edu
authors: John A
authors: JA
authors: Thompson
authors: Ernesto
authors: E
authors: Salcedo
authors: Diego
authors: D
authors: Restrepo
authors: Thomas E
authors: TE
authors: Finger
mesh_terms: D000679:Amygdala / Q000166:cytology* / Q000378:metabolism; D000818:Animals; D005260:Female; D007150:Immunohistochemistry; D008297:Male; D040542:Mechanotransduction, Cellular / Q000502:physiology; D051379:Mice; D008810:Mice, Inbred C57BL; D018613:Microscopy, Confocal; D009830:Olfactory Bulb / Q000166:cytology* / Q000378:metabolism; D009833:Olfactory Pathways / Q000166:cytology / Q000378:metabolism; D018034:Olfactory Receptor Neurons / Q000166:cytology* / Q000378:metabolism; D050053:TRPM Cation Channels / Q000096:biosynthesis*
chemical_list: D050053:TRPM Cation Channels; C498617:Trpm5 protein, mouse