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UBC Theses and Dissertations

Electrical stimulation of reward sites in the ventral tegmental area of the rat increases dopamine transmission in the nucleus accumbens as measured by in vivo microdialysis Fiorino, Dennis Frank


In vivo microdialysis with HPLC-ED was used to measure dopamine (DA),3,4-dihydroxyphenylacetic acid (DOPAC), homovanillic acid (HVA) and 5-hydroxyindoleacetic acid (5-HIAA) in the nucleus accumbens of the rat, prior to, during, and after 15-min periods of electrical brain-stimulation at sites in the ventral tegmental area (VTA) that supported intracranial self-stimulation (ICSS). In the first experiment, both ICSS and yoked-stimulation of the VTA evoked significant increases in extracellular concentrations of DA, its metabolites, and 5-HIAA.Comparable results from ICSS and yoked groups were interpreted as evidence that the rewarding properties of VTA stimulation were a causal factor in the elevated DA transmission in the nucleus accumbens, rather than intense operant behavior. Further evidence for this hypothesis came from a second set of data in which changes in extracellular DA levels during the measurement of rate/intensity functions for ICSS were positively correlated. 5-HIAA concentrations also increased during ICSS but these changes were not correlated with either ICSS rate or current intensity, suggesting that changes in serotonin metabolism were unlikely to subserve brain-stimulation reward in the VTA. These results provide further evidence that stimulated mesolimbic DA release is a sufficient condition for reward.

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