Dopamine depletion with tyrosine-free amino acid mixture in nucleus accumbuns of awake rats (2013)

Undergraduate: Sarah Taylor

Faculty Advisor: Donita Robinson
Department: Biology

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Dopamine is a neurotransmitter implicated in reward/motivational neurocircuitry which includes a primary pathway connecting the ventral tegmental area (VTA) and nucleus accumbens (NAc). Prior studies have revealed that dopaminergic VTA neurons projecting to the NAc are implicated in cue-response behavior in humans and rats. Microdialysis rodent studies have shown that the administration of an amino acid mixture lacking tyrosine (and its precursor, phenylalanine) (Tyr/Phe-) results in temporary depletion of tonic dopamine in NAc. This study tested the effectiveness of the Tyr/Phe- mixture on phasic dopamine transient activity in same brain region. We hypothesized that the Tyr/Phe- mixture would decrease the frequency of spontaneous dopamine transients and the amplitude of electrically evoked dopamine release in the NAc of awake rats. We used fast scan cyclic voltammetry (FSCV) to measure both spontaneous dopamine transients and electrically evoked dopamine release in the NAc of rats at baseline and after injection of Tyr/Phe- mixture. We found that administration of the Try/Phe- mixture led to a decrease in both the number of dopamine transients and the amplitude of electrically evoked dopamine. The verification of the mixture¿s effectiveness in awake rats allows further studies to be conducted on role of dopamine in cue-response behavior in both rats and human subjects.