Lack of Effect of Tyrosine Depletion on Mood in Recovered Depressed Women

Abstract

The role of dopamine (DA) pathways in the pathophysiology of depressive disorder is poorly understood. However, because DA plays a key role in motivational behavior, it is important to study in a disorder characterized by anhedonia, lack of energy and psychomotor retardation. A recently developed dietary manipulation ('tyrosine (TYR) depletion') offers a novel method to assess the role of DA in major depression. We studied 15 euthymic women with a past history of recurrent depression, who received a 74 g amino-acid drink lacking TYR and phenylalanine (PHE) (TYR-free) and a balanced (BAL) amino acid drink on two separate occasions in a double-blind, random-order, crossover design. Plasma prolactin levels rose following the TYR-free drink relative to the balanced mixture, while performance on a spatial recognition memory task was impaired. However, relative to the BAL drink, the TYR-free drink did not lower objective or subjective measures of mood. We conclude that as in healthy volunteers, TYR depletion in euthymic subjects, with a past history of major depression, attenuated DA function, as reflected in increased plasma prolactin levels and decreased spatial memory performance. However ratings of depression were unaffected, suggesting that disruption of dopaminergic function by this manipulation does not induce a lowering of mood in individuals vulnerable to depression.

Dopamine and light: dissecting effects on mood and motivational states in women with subsyndromal seasonal affective disorder

“…45,51 Notably, no significant correlations between changes in POMS energetic-tired scores and PR results were found for either light condition (r < 0.218, p > 0.15). While it cannot be ruled out that the effect of APTD on PR breakpoints may have reflected fatigue or psychomotor retardation, previous APTD studies reported no effect of APTD on response time or latency in either recovered depressed patients 48,52 or healthy controls, 53 whereas a significant increase in apathy has been observed. 53 Our observations support this finding and suggest that motivation to obtain reward and subjective experience of energy are both DA-related but may be independent effects.…”

Dietary Tyrosine/Phenylalanine Depletion Effects on Behavioral and Brain Signatures of Human Motivational Processing

“…The lack of a main effect of TPD on POMS-TMD ratings or MID task cue affective ratings also reflects negative findings in the literature when TPD is administered to normal controls (eg, Lythe et al, 2005;Coupland et al, 2001;Nagano-Saito et al, 2012) and even in subjects with histories of depression who were in remission at the time of testing (McTavish et al, 2004(McTavish et al, , 2005. There were large individual differences in absolute TMD ratings on each study day, however, and in net difference scores in POMS-TMD between mixture conditions.…”

‘It's not over when it's over’: persistent neurobiological abnormalities in recovered depressed patients

“…However, dietary depletion of tyrosine, the amino acid precursor of noradrenaline and dopamine, does not (McTavish et al 2005). While AMPT diminishes both noradrenaline and dopamine synthesis, the effects of tyrosine depletion appear limited to dopamine activity, perhaps because of the greater utilization of tyrosine by dopaminergic neurones (McTavish et al 1996).…”