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Brain glutamate metabolism during hypoxia and peripheral chemodenervation
B Hoop1, M R Masjedi, V E Shih
1Medical Services (Pulmonary and Critical Care Unit), Massachusetts General Hospital, Harvard Medical School, Boston 02114.
Journal of Applied Physiology (Bethesda, Md. : 1985)
|July 1, 1990
Summary
Hypoxia reduces the brain
Area of Science:
- Neuroscience
- Physiology
- Biochemistry
Background:
- Glutamate influences ventilation and neural excitability.
- Hypoxia impacts ventilatory drive, cerebral perfusion, and glutamate metabolism.
- Peripheral chemoreceptors play a role in the hypoxic ventilatory response.
Purpose of the Study:
- To investigate the effects of hypoxia and peripheral chemodenervation on cerebrospinal fluid (CSF) glutamate transfer rates.
- To assess alterations in brain glutamate metabolism under hypoxic conditions in intact and chemodenervated dogs.
Main Methods:
- Used pentobarbital-anesthetized dogs, subjected to normoxia and hypoxia (10-12% O2).
- Performed chemodenervation by sectioning carotid body nerves and vagi.
- Measured CSF transfer rates of 13NH4+ and [13N]glutamine, reflecting glutamate-glutamine metabolism, using in vivo tracer techniques.
Main Results:
- Hypoxia reduced the maximal glial glutamine efflux rate (jm) in intact dogs.
- Chemodenervation significantly decreased jm during hypoxia compared to intact animals.
- Hypoxia increased cerebral cortical glutamate concentration, particularly in denervated dogs.
Conclusions:
- Peripheral chemoreceptors are crucial for maintaining glutamate-glutamine metabolism during hypoxia.
- Hypoxia, especially without peripheral chemoreceptor input, alters central glutamate homeostasis.
- Findings suggest a link between peripheral chemoreception, central glutamate, and ventilatory control during hypoxia.