Dopamine depletion with tyrosine-free amino acid mixture in nucleus accumbens of rats (2014)

Undergraduate: Sarah Taylor

Faculty Advisor: Donita Robinson
Department: Biology

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Dopamine (DA) 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 DA in the NAc. This study tested the effectiveness of the Tyr/Phe- mixture on phasic DA transient activity in same brain region. We hypothesized that the Tyr/Phe- mixture would decrease the frequency and amplitude of spontaneous DA transients in the NAc of rats while a control mixture containing tyrosine and phenylalanine (Tyr+/Phe+) would have no effect on spontaneous DA release. We used fast scan cyclic voltammetry (FSCV) to measure spontaneous DA transients release in the NAc of rats at baseline and after injection of the Tyr/Phe- or Tyr+/Phe+ mixture. We found that administration of the Try/Phe- mixture led to a decrease in both the number and amplitude of DA transients while administration of the Tyr+/Phe+ mixture had no effect of frequency of DA transients. The verification of the mixture¿s effectiveness in rats allows further studies to be conducted on role of DA in cue-response behavior in both rats and human subjects.