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A glycogen phosphorylase inhibitor selectively enhances local rates of glucose utilization in brain during sensory stimulation of conscious rats: implications for glycogen turnover
Author(s) -
Dienel Gerald A.,
Ball Kelly K.,
Cruz Nancy F.
Publication year - 2007
Publication title -
journal of neurochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.75
H-Index - 229
eISSN - 1471-4159
pISSN - 0022-3042
DOI - 10.1111/j.1471-4159.2007.04595.x
Subject(s) - glycogen , glycogen phosphorylase , medicine , stimulation , endocrinology , glycogen branching enzyme , chemistry , glycogen synthase , stimulus (psychology) , biology , psychology , psychotherapist
Glycogen is degraded during brain activation but its role and contribution to functional energetics in normal activated brain have not been established. In the present study, glycogen utilization in brain of normal conscious rats during sensory stimulation was assessed by three approaches, change in concentration, release of 14 C from pre‐labeled glycogen and compensatory increase in utilization of blood glucose (CMR glc ) evoked by treatment with a glycogen phosphorylase inhibitor. Glycogen level fell in cortex, 14 C release increased in three structures and inhibitor treatment caused regionally selective compensatory increases in CMR glc over and above the activation‐induced rise in vehicle‐treated rats. The compensatory rise in CMR glc was highest in sensory‐parietal cortex where it corresponded to about half of the stimulus‐induced rise in CMR glcf in vehicle‐treated rats; this response did not correlate with metabolic rate, stimulus‐induced rise in CMR glc or sequential station in sensory pathway. Thus, glycogen is an active fuel for specific structures in normal activated brain, not simply an emergency fuel depot and flux‐generated pyruvate greatly exceeded net accumulation of lactate or net consumption of glycogen during activation. The metabolic fate of glycogen is unknown, but adding glycogen to the fuel consumed during activation would contribute to a fall in CMR O2 /CMR glc ratio.