P50). It is probable
that this period of final myelination corresponds to a time of hightened
metabolic activity in white matter. The tolerance of CNS white matter to
energy deprivation can be categorized into four stages that are correlated
with specific developmental features: 1) Premyelination (P0-P4), highly
tolerant to anoxia, aglycemia and combined anoxia/aglycemia. 2) Early
myelination (P5-P20), partially tolerant of anoxia and aglycemia but not to
combined anoxia/aglycemia. 3) Late myelination (P21-P49), very low tolerance
of anoxia, aglycemia and combined anoxia/aglycemia. 4) Mature (>P50), low
tolerance of anoxia, aglycemia and combined anoxia/aglycemia. The relative
resistance of optic nerve function to glucose withdrawal in the presence of
oxygen, compared to glucose withdrawal in the absence of oxygen, is presumably
due to the presence of oxygen-dependent energy reserves such as astrocytic
glycogen, amino-acids and phospholipids.
Received 21 February 1997; accepted in final form 17 September 1997.
APS Manuscript Number J156-7.
Article publication pending J. Neurophysiol.
ISSN 1080-4757 Copyright 1997 The American Physiological Society.
Published in APStracts on 7 October 1997