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Organization of glomeruli in the main olfactory bulb of Xenopus laevis tadpoles
Author(s) -
Nezlin Leonid P.,
Heermann Stephan,
Schild Detlev,
Rössler Wolfgang
Publication year - 2003
Publication title -
journal of comparative neurology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.855
H-Index - 209
eISSN - 1096-9861
pISSN - 0021-9967
DOI - 10.1002/cne.10709
Subject(s) - biology , neuropil , xenopus , olfactory bulb , olfactory system , glomerulus , neuroscience , olfactory receptor , ultrastructure , anatomy , central nervous system , endocrinology , biochemistry , gene , kidney
Structural and functional investigations were carried out to study olfactory glomeruli in the main olfactory bulb (OB) in tadpoles of the clawed frog, Xenopus laevis . Calcium imaging of odor response patterns of OB neurons revealed that the synapses within the glomeruli are functional. Tracing axons of individual olfactory receptor neurons (ORNs), dendrites of mitral/tufted (M/T) cells and processes of periglomerular interneurons indicate that the glomerular architecture is solely determined by terminal branches of ORN axons and tufts of M/T primary dendrites. The small population of periglomerular neurons forms wide‐field arborizations that always extend over many glomeruli, enter the glomeruli, but lack any glomerular tufts. Antibodies to synaptophysin indicate a high density of synapses within glomeruli, which was further confirmed at the ultrastructural level and quantified to approximately 0.5 synaptic sites per μm 2 . Combining immunocytochemistry and ultrastructural investigations, we show that glomeruli in Xenopus laevis tadpoles lack any cellular borders. Glomeruli are surrounded neither by periglomerular somata nor by glial processes. Taken together, our results demonstrate that olfactory glomeruli in Xenopus laevis tadpoles (1) are fully functional, (2) are spheroidal neuropil aggregations of terminal tufts of ORNs and tufts of primary dendrites of M/T cells, and (3) are not enwrapped by a border formed by juxtaglomerular cells. J. Comp. Neurol. 464:257–268, 2003. © 2003 Wiley‐Liss, Inc.