Central Olfactory Pathway Research Articles

Axon pathway boundaries in the developing brain. I. Cellular and molecular determinants that separate the optic and olfactory projections

When optic fibers first approach the chiasmatic region of the diencephalon in the chick embryo on days 3 and 4 (E3-4), they rarely grow rostrally into the olfactory region of the telencephalon. Conversely, olfactory tract axons grow as far as, but never cross the diencephalic/telencephalic (D/T) boundary to enter the optic chiasm. In this study, a region of specialized neuroepithelium, originally named the "knot" in mouse by Silver (1984), has been identified at the D/T border of chick embryos. At pre-axonal stages, the presumptive knot region undergoes a cataclysmic cell death, with concomitant phagocytosis of necrotic debris by the remaining cells. When fibers subsequently appear in the chiasm and olfactory tracts, the knot consists of a very dense, interwoven cluster of non-neuronal cells that lack marginal radial processes, and whose cell bodies directly abut the glial limiting membrane. Thus, the morphology of the knot is in sharp contrast to the cell body-free marginal zone and endfoot regions along which axons tend to grow. In addition, we found that the neural cell adhesion molecule (N-CAM), which is expressed on neuroepithelial cell processes within the central optic and olfactory pathways, is not present on cells in the knot region during periods of axon growth. These results suggest that the knot, through its elimination of the marginal zone processes, absence of large extracellular spaces, and relative absence of adhesion molecules, functions as an axon-refractory barrier that effectively separates the optic and olfactory projections.

Mitral cell degeneration and sensory function in the neurological mutant mouse Purkinje cell degeneration (PCD)

Selective degeneration of mitral cells, the principal relay neuron in the central olfactory pathway, is described in the mutant mouse Purkinje cell degeneration (PCD). Concomitant effects are described in adjacent layers of the olfactory bulb which suggest a reorganization of local neuronal circuits. The 2-deoxyglucose technique produced results which suggested that the topographical distribution of sensory afferent input to the bulb was not affected.

Immunocytochemical localization of LHRH in central olfactory pathways of hamster

Immunocytochemical localization of LHRH in central olfactory pathways of hamster