Plasma -tryptophan/neutral amino acid ratio and dexamethasone suppression in depression

Tryptophan (Trp), an indispensable amino acid for dogs, is the precursor of serotonin, a neurotransmitter with a variety of effects throughout the body, including the ability to modulate cardiac and pulmonary activity. This study aimed to investigate the effects of a 12-week incremental exercise regimen and supplemental dietary Trp on heart rate (HR) and respiratory rate (RR) in client-owned sled dogs. Sixteen Siberian huskies were randomly allocated to either treatment or control diet groups. Both groups were fed a control diet (Trp to large neutral amino acid ratio of 0.047:1); however, treatment dogs received a Trp supplement to achieve a Trp to large neutral amino acid ratio of 0.075:1. Every three weeks, external telemetry equipment was used to non-invasively measure and record HR and RR at a resting, working, and post-exercise state in a controlled exercise challenge. A mixed model was used to test differences between diet, activity parameter, and week. Dietary Trp supplementation had no effect on HR or RR. Independent of diet, resting, working, post-exercise HR, and time to recover post-exercise HR decreased from week −1 to week 11 (p < 0.05). Resting HR had the greatest reduction from week −1 to week 11 (21%, p < 0.05). Working RR did not change with exercise (p > 0.10), but rRR and postRR decreased from week −1 to week 11 (p < 0.05). These data suggest that the exercise regimen the dogs were subjected to may have positively impacted the dogs’ capacity to sustain aerobic exercise, whereas Trp supplementation had no effect on HR or RR.

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Plasma tryptophan to large neutral amino acid ratios in depressed and normal subjects

Journal of Affective Disorders ◽

10.1016/0165-0327(90)90003-q ◽

1990 ◽

Vol 19 (1) ◽

pp. 9-14 ◽

Cited By ~ 14

Author(s):

Mark J. Russ ◽

Sigurd H. Ackerman ◽

Miriam Banay-Schwartz ◽

Richard D. Shindledecker ◽

Smith Gerard P.

Keyword(s):

Amino Acid ◽

Normal Subjects ◽

Neutral Amino Acid ◽

Large Neutral Amino Acid ◽

Plasma Tryptophan

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Plasma tyrosine/neutral amino acid ratio correlated with clinical response to nortriptyline in endogenously depressed patients

Journal of Affective Disorders ◽

10.1016/0165-0327(85)90052-7 ◽

1985 ◽

Vol 9 (3) ◽

pp. 223-229 ◽

Cited By ~ 17

Author(s):

S.E. Møller ◽

K. Ødum ◽

L. Kirk ◽

M. Bjerre ◽

F. Fog-Møller ◽

...

Keyword(s):

Amino Acid ◽

Clinical Response ◽

Neutral Amino Acid ◽

Depressed Patients ◽

Acid Ratio ◽

Plasma Tyrosine

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A High Carbohydrate, Protein-Free Meal, either at Breakfast or in the Evening Does not Alter Plasma Tryptophan to Large Neutral Amino Acid Ratios in Healthy Men

Progress in Tryptophan and Serotonin Research ◽

10.1515/9783111641546-083 ◽

1984 ◽

pp. 579-582 ◽

Cited By ~ 4

Keyword(s):

Amino Acid ◽

Neutral Amino Acid ◽

Large Neutral Amino Acid ◽

Healthy Men ◽

Plasma Tryptophan ◽

High Carbohydrate

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Reversed diurnal variation in depression: associations with a differential antidepressant response, tryptophan:large neutral amino acid ratio and serotonin transporter polymorphisms

Psychological Medicine ◽

10.1017/s0033291704003861 ◽

2005 ◽

Vol 35 (4) ◽

pp. 511-517 ◽

Cited By ~ 18

Author(s):

PETER R. JOYCE ◽

RICHARD J. PORTER ◽

ROGER T. MULDER ◽

SUZANNE E. LUTY ◽

JANICE M. McKENZIE ◽

...

Keyword(s):

Amino Acid ◽

Diurnal Variation ◽

Serotonin Transporter ◽

Neutral Amino Acid ◽

Antidepressant Response ◽

Bipolar Ii Disorder ◽

Acid Ratio ◽

Bipolar Ii ◽

Diurnal Variation Of Mood ◽

Serotonergic Antidepressant

Background. Although diurnal variation of mood is a widely recognized symptom of depression, the clinical, neurobiological and psychopharmacological significance of this symptom has not previously been reported.Method. A total of 195 depressed out-patients underwent a detailed clinical and neurobiological assessment, and were then randomized to treatment with either fluoxetine or nortriptyline.Results. Of the 195 depressed patients, 62 had a pattern of reversed diurnal variation (i.e. worse in the evening). Those with reversed diurnal variation had a poorer response to a serotonergic antidepressant, were less likely to have bipolar II disorder, had a higher tryptophan:large neutral amino acid ratio and had different allele frequencies of the polymorphisms in the promoter region of the serotonin transporter.Conclusions. These findings raise the possibility of serotonergic influence on diurnal variation, and that the symptom of reversed diurnal variation is of relevance to antidepressant prescribing.

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