Chunk #18 — Results — Differential dopamine release dynamics in the core versus shell relative to cocaine-reinforced responding during self-administration
In Experiment 1 (n = 8 rats), the precise temporal characteristics of rapid dopamine release events relative to the reinforced response for intravenous cocaine during self-administration was compared across the NAc core and shell using recordings every 100 ms. The carbon-fiber electrode was inserted into the desired region of the NAc via a micromanipulator, and its position was adjusted until high concentrations of dopamine during electrical stimulation were observed. This procedure was used to ensure the electrode was located among dopamine terminals (Wightman et al., 2007). Figure 1A shows a color representation of a set of background-subtracted cyclic voltammograms and the corresponding [DA] changes in the NAc core time-locked to a single operant response. Consistent with our prior reports (Phillips et al., 2003b; Stuber et al., 2005a; Stuber et al., 2005b), dopaminergic signals at the lever press for intravenous cocaine in the core had two distinct components; an initial increase in dopamine within seconds before the response followed by a larger more sustained increase following response completion. As in prior studies, the pre-response increase began approximately 1 s before the
