Kinetics of the inhibition of axonal defasciculation and arborization mediated by carbohydrate markers in the embryonic leech.
We studied carbohydrate interactions that mediate the targeting of sensory afferents in the synaptic neuropil of segmental central nervous system (CNS) ganglia in the embryonic leech. First, we determined the rate of sensory afferent development in vivo, and then we devised a culture system that permits the normal patterning of their projections in the CNS and PNS to proceed at 92% the normal rate. Using this in vitro system, we analyzed the mannose-specific recognition that mediates the defasciculation and arborization of sensory afferents in the CNS neuropil after they have tracked through peripheral nerves as a tight axon bundle. Sensory afferent defasciculation and arborization in the neuropil were inhibited by culturing embryos in Fab fragments directed against the mannose-containing surface epitope of sensory afferents. We demonstrate that the rate at which separately extending axons or their branches are lost from the neuropil can be modeled by a first-order decay process. These kinetic studies indicate that the loss of each separately extending axon or branch is an independent event. This suggests that sensory afferent projections extend autonomously across the target region in the search of their appropriate postsynaptic partners.
Song
J
J
Department of Physiology, Michigan State University, East Lansing 48824, USA.
Zipser
B
B
D000818:Animals; D002450:Cell Communication / Q000187:drug effects; D002455:Cell Division; D002478:Cells, Cultured; D007140:Immunoglobulin Fab Fragments / Q000494:pharmacology; D007865:Leeches / Q000196:embryology*; D008358:Mannose / Q000276:immunology / Q000378:metabolism*; D009420:Nervous System / Q000196:embryology*; D009424:Nervous System Physiological Phenomena; D009475:Neurons, Afferent / Q000166:cytology / Q000187:drug effects / Q000502:physiology*; D017729:Presynaptic Terminals / Q000378:metabolism*
D007140:Immunoglobulin Fab Fragments; D008358:Mannose