The effect of a tryptophan-depleted diet on voluntary exercise in mice

The essential amino acid tryptophan serves as the precursor to serotonin, a neurotransmitter which regulates hunger and satiety, promotes sleep, relieves depression, and is found in elevated levels following exercise. A quantitative deficit in serotonin or abnormality in its mode of action is thought to be one cause behind several psychological disorders such as depression, eating disorders, and obsessive-compulsive disorder. A decrease in dietary tryptophan has been shown to decrease serotonin production thereby, theoretically, producing the effects of a hyposerotonergic state. The purpose of this study was to further elucidate serotonin’s role in influencing an individual’s activity level by inducing a decrease in this neurotransmitter via a tryptophan-depleted diet. Specifically, 40 individually-housed mice were divided into four groups of ten. Group C received a control diet while group CW consumed a control diet and had access to a running wheel. Group E received a diet low in tryptophan while group EW was given the experimental diet and had access to a running wheel. A seven-day adaptation period was followed by a ten-day experimental period during which time groups E and EW received the experimental diet. Only the food consumption of group EW increased significantly over time. Running wheel activity was monitored every 12 hours corresponding to a light/dark cycle. An analysis of this data revealed a significant post-test rise in the activity levels of the mice in group EW compared to the activity of group CW. The wheel revolutions per 24 hours dropped by 17% in group CW while group EW’s revolutions increased by 19%. Furthermore, while revolutions increased from pre-test to post-test in only four out of 10 control subjects, they increased in all nine of the experimental subjects. It seems likely that the tryptophan depletion caused a decrease in brain serotonin levels. Therefore, the results of this experiment support the theory that the mice on a low-tryptophan diet increased their activity in a subconscious effort to normalize serotonin levels which would bring about a return of the desirable effects of this neurotransmitter.

Name thesis:degree_name

Master of Science

Level thesis:degree_level

masters

Discipline thesis:degree_discipline

Human Nutrition, Foods, and Exercise

Department dc:contributor.department

Human Nutrition, Foods, and Exercise

Grantor dc:publisher

Virginia Tech

Year dc:date.issued

1996

Author dc:creator

• DeVerter, Ann M.

Chair dc:contributor.committeechair

• Williams, Jay H.

Committee members dc:contributor.committeemember

• Denbow, D. Michael
• Thomas, Elizabeth A.

• serotonin

Statement dc:rights

• In Copyright

Licence dc:rights.uri

• http://rightsstatements.org/vocab/InC/1.0/

Language dc:language.iso

en

Dc Identifier Other

etd-05092009-040603

OAI identifier oai:identifier

oai:vtechworks.lib.vt.edu:10919/42557