Anatomical studies show that in the nigrostriatal system, dopamine neurons have axons that arborize, resulting in terminals that are clustered in multiple locations (Prensa & Parent, 2001). Moreover, dopaminergic clusters make synaptic contact with the necks of the dendritic spines on MSNs in the striatum (Surmeier et al., 2007), and a similar architecture exists in the NAc (Shen et al., 2008). MSNs in the NAc have cell bodies with a radius of ~ 10 μm, and their dendritic fields are approximately oval and extend > 250 μm (van Dongen et al., 2008). DAT is located ubiquitously on dopaminergic terminals and thereby provides a index of the density and distribution of dopamine terminals (Nirenberg et al., 1997). Mathematical models suggest that an electrode should be within five times the radius of the cell body for a measurable extracellular signal (Prochazka, 1984). Furthermore, from the uptake rate of dopamine by the DAT, we can estimate the distance it can diffuse from the release sites to the electrode. Dopamine has a half life of ~0.05 s in the NAc, therefore, its concentration will
