Multi-site analysis of dopamine uptake in the somatosensory cortex

Voltammetry has been used as a method to measure the concentration of monoaminergic neurotransmitters in-vivo. The standard electrode used with voltammetry has been carbon fiber microelectrodes. Despite the advantages of using carbon as a sensing element, carbon fiber microelectrodes have only one site to record the extracellular concentration of neurotransmitters. Studies have shown that the concentration of neurotransmitters, such as dopamine, varies across small regions of the brain (less than Imm). To study the varying concentration of dopamine, the recording sites of a ceramic-based multi-site electrode was coated with carbon and deployed in the somatosensory cortex of a rat. Known concentrations of dopamine were pressure injected and the diffusion curve, which is the change in concentration over time, was recorded. From the falling phase of the diffusion curve, the initial rate of clearance was measured. The initial rates of clearance from the different recording sites in the somatosensory cortex were compared to a model that used the standard diffusion equation with uptake. The results show that the in-vivo data does not follow the prediction of the model providing an interesting insight to the uptake of monoamines across the different layers of the somatosensory cortex.