Figure 6.

Dopamine transient half-width following administration of morphine or oxycodone. A. Average transient half-width over the 15 min recording periods following saline controls and groups receiving saline plus cumulative doses (Low = 0.1 mg/kg, Medium = 0.5 mg/kg, High = 1.0 mg/kg; i.v.) of either morphine or oxycodone. Neither the low nor the high doses of morphine significantly evoked an overall increase in transient half-width during the entire 15 min recording intervals. However, the medium dose of morphine caused a significant increase in half-width above saline controls. Conversely, all doses of oxycodone failed to alter mean transient half-width. B. A representative [DA] trace (that corresponds to the color plot shown in Fig 4B) showing the recording ~2 min following high dose morphine infusion within the NAc shell, and C. a similar [DA] trace following a high dose oxycodone infusion. D and E. Mean transient half-width was binned every min for the duration of the 15 min recording interval and compared to the average half-width post-control saline infusion. D. Morphine-evoked increases in DA transient half-width measured across 1 min time bins shows that only subjects that received low dose morphine infusion failed to increase transient half-width. Following medium and high dose infusions of morphine, transient half-width was significantly increased at the 3 min mark following the medium dose of morphine and during the first min following the high dose. There was a trend towards significance during the first min following the medium dose of morphine. E. At all tested doses, oxycodone failed to increase transient half-width. Error bars indicate SEM. * indicates statistically significant increases (p < 0.05).