Carbon fiber microelectrodes with multiple sensing elements for in vivo voltammetry

Electrically evoked dopamine release was monitored in the striatum of anesthetized rats using voltammetric microelectrode assemblies with two to four separately addressable carbon fiber sensing elements. The sensing elements were disk-shaped, had a diameter of about 1 microm, and were separated from each other by less than 15 microm. The microelectrodes were used to monitor extracellular dopamine at multiple depths beneath the brain surface during electrical stimulation of the medial forebrain bundle. When the sensing elements were 10-15 microm apart, the stimulus responses at each element were distinct, suggesting that each response was representative of a distinct recording site. The possibility of performing measurements at distinct but closely spaced sites provides a potential route to high spatial resolution information about extracellular events. On the other hand, when the individual sensing elements were about 1 microm apart, similarities between the observed stimulus responses suggest that the multiple elements were recording from a single site. The ability to perform multiple chemical measurements at a single site presents several opportunities for new approaches to the in vivo study of neurochemistry.