Correlation of local changes in extracellular oxygen and pH that accompany dopaminergic terminal activity in the rat caudate-putamen.
Terminal activity causes an increase in local cerebral blood flow that can be quantified by measuring the accompanying increase in tissue oxygen. Alkaline pH changes can also follow neuronal activation. The purpose of these studies was to determine whether these changes in extracellular oxygen and pH correlate. Fast-scan cyclic voltammetry was used to detect changes in dopamine, pH and oxygen levels simultaneously in the caudate-putamen after electrical stimulation of the substantia nigra in anesthetized rats. The biphasic increases in oxygen and pH followed similar time courses, and were delayed a few seconds from the immediate release and uptake of dopamine. The changes following administration of neurotransmitter receptor antagonists as well as agents that modulate blood flow were identical for oxygen and pH. Two distinct mechanisms were identified that give rise to the oxygen and pH changes: blood vessel dilatation caused by nitric oxide synthesis after muscarinic receptor activation and adenosine receptor activation. We conclude that changes in blood flow accompanying terminal activity cause alkaline pH shifts by the rapid removal of carbon dioxide, a component of the extracellular brain buffering system.
Venton
B Jill
BJ
Department of Chemistry and Neuroscience Center, University of North Carolina, Chapel Hill, USA.
Michael
Darren J
DJ
Wightman
R Mark
RM
D000818:Animals; D001783:Blood Flow Velocity / Q000187:drug effects / Q000502:physiology; D002421:Caudate Nucleus / Q000378:metabolism*; D002560:Cerebrovascular Circulation / Q000187:drug effects / Q000502:physiology; D004298:Dopamine / Q000378:metabolism*; D004563:Electrochemistry; D004567:Electrodes, Implanted; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005110:Extracellular Space / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D008297:Male; D008839:Microelectrodes; D010084:Oxidation-Reduction; D010100:Oxygen / Q000378:metabolism*; D017729:Presynaptic Terminals / Q000378:metabolism*; D011699:Putamen / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D017981:Receptors, Neurotransmitter / Q000037:antagonists & inhibitors; D009435:Synaptic Transmission / Q000502:physiology; D013806:Theophylline / Q000494:pharmacology; D014666:Vasomotor System / Q000187:drug effects
D004791:Enzyme Inhibitors; D017981:Receptors, Neurotransmitter; D013806:Theophylline; D010100:Oxygen; D004298:Dopamine