Simultaneous measurement of oxygen and dopamine: Coupling of oxygen consumption and neurotransmission

Abstract

Fast-scan cyclic voltammetry was used to simultaneously measure increases in dopamine concentration and decreases in O 2 concentration evoked by brief electrical stimulation (two pulses at 10 Hz) in slices of rat caudate nucleus. Dopamine concentration began increasing immediately after the first pulse and reached a maximum within 200 ms of stimulation. The O 2 concentration began to decrease 300–700 ms after onset of stimulus. Responses for both dopamine and O 2 were dependent on external Ca 2+ and were Cd 2+ and tetrodotoxin sensitive. Only the O 2 response was sensitive to CN − (0.15 mM). At short times after exposure to 50 μM ouabain, electrically stimulated dopamine overflow was increased by 150% and electrically stimulated changes in O 2 concentration were unaffected. Maximum dopamine concentration was increased 28% by sulpiride (2 μM), 78% by l-DOPA (60 μM), 105% by nomifensine (10 μM) and unaffected by nialamide (10 μM). Maximum decrease in O 2 concentration was increased by 25% by sulpiride and unaffected by nialamide, l-DOPA, or nomifensine. The decreases in O 2 concentration are indicative of increased O 2 consumption and are a measure of oxidative energy production evoked by electrical stimulation. The increase in dopamine is due to the release of dopamine balanced by uptake and serves as an indication of neurotransmitter activity. The results indicate that increases in oxidative energy production following electrical stimulation are dependent on external Ca 2+ entry through Cd 2+-sensitive channels. Possible mechanisms for this coupling are discussed.