We are characterizing the electrochemistry of adenosine at carbon-fiber microelectrodes. While dopamine has been extensively studied using carbon-fiber microelectrodes, the technique has not been widely applied to many of other neurochemicals. Adenosine is a neuromodulator in the brain that has a variety of actions including regulation of cerebral blood flow, modulation of neurotransmission, and protection against neuronal injury during stroke. No reliable method currently exists for electrochemical detection of adenosine in vivo. Direct detection of adenosine using cyclic voltammetry at carbon-fiber microelectrodes will be examined. The strategy is to take advantage of the adsorption that occurs due to molecular interactions of the analyte with surface groups on the electrode, such as oxides. Adenosine, which contains a primary amine group, is expected to adsorb to a carbon-fiber surface. Simultaneous detection of adenosine, dopamine, and oxygen levels should be possible with cyclic voltammetry since they have different oxidation and reduction potentials. The sensor will be used to characterize adenosine release in the brain. Adenosine release during neurotransmission and models of stroke will be investigated.
In vivo studies of the effects of adenosine. Dopamine, pH, and oxygen changes were measured before (left) and after (right) administration of theophylline, an adenosine receptor antagonist. Applied voltage is the y-axis, elapsed time the x-axis and measured current is in color. The top traces, taken from the color plots, show concentration changes over time. Adenosine receptor antagonism reduces the second peak of oxygen changes.
Pathways
of
adenosine formation. Adenosine can be
formed intracellulary and then transported out of the neuron or
extracellulary
after the breakdown of released
ATP.
