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Astrocyte activation in vivo during graded photic stimulation
Author(s) -
Dienel Gerald A.,
Schmidt Kathleen C.,
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.1471-4159.2007.04859.x
Subject(s) - stimulation , astrocyte , stimulus (psychology) , extracellular , neuroscience , metabolism , in vivo , premovement neuronal activity , photic stimulation , neurotransmission , sensory stimulation therapy , biology , medicine , chemistry , endocrinology , biophysics , biochemistry , central nervous system , psychology , receptor , visual perception , microbiology and biotechnology , perception , psychotherapist
Astrocytes have important roles in control of extracellular environment, de novo synthesis of neurotransmitters, and regulation of neurotransmission and blood flow. All of these functions require energy, suggesting that astrocytic metabolism should rise and fall with changes in neuronal activity and that brain imaging can be used to visualize and quantify astrocytic activation in vivo . A unilateral photic stimulation paradigm was used to test the hypothesis that graded sensory stimuli cause progressive increases in the uptake coefficient of [2‐ 14 C]acetate, a substrate preferentially oxidized by astrocytes. The acetate uptake coefficient fell in deafferented visual structures and it rose in intact tissue during photic stimulation of conscious rats; the increase was highest in structures with monosynaptic input from the eye and was much smaller in magnitude than the change in glucose utilization (CMR glc ) by all cells. The acetate uptake coefficient was not proportional to stimulus rate and did not correlate with CMR glc in resting or activated structures. Simulation studies support the conclusions that acetate uptake coefficients represent mainly metabolism and respond to changes in metabolism rate, with a lower response at high rates. A model portraying regulation of acetate oxidation illustrates complex relationships among functional activation, cation levels, and astrocytic metabolism.