Acute tryptophan depletion induced by a gelatin-based mixture impairs object memory but not affective behavior and spatial learning in the rat.
One manner to study the role of serotonin (5-HT) in behavioral functions is through nutritional manipulation of its precursor tryptophan (TRP). By means of the method of acute TRP depletion, plasma TRP levels can be reduced in a reversible way in both humans and rats. In the present study a TRP-free protein-carbohydrate mixture was used to investigate the behavioral effects of lowering TRP and 5-HT concentrations in adult male rats. These animals were tested in models of anxiety (open field, home cage emergence test), depression (forced swimming test) and cognition (object recognition test and Morris water escape test). The TRP-free protein-carbohydrate mixture substantially reduced the ratio TRP/SigmaLNAA within 2 and 4 h by 75 and 60%, respectively. It was found that 4 h after administration, the treatment did not affect anxiety-related behavior nor did it cause depressive-like behavior. Also, no treatment effect was found on spatial learning performance in a Morris water escape test. On the other hand, performance in an object recognition test was clearly impaired after TRP depletion. Taken together, these data suggest that acute lowered central 5-HT levels are not associated with changes in affective behavior (i.e. anxiety and depression), but do impair object memory in adult rats.
Lieben
Cindy K J
CK
Department of Psychiatry and Neuropsychology, Division of Neuroscience, University Maastricht, P.O. Box 616, 6200 MD Maastricht, The Netherlands. c.lieben@np.unimaas.nl
van Oorsouw
Kim
K
Deutz
Nicolaas E P
NE
Blokland
Arjan
A
D000339:Affect / Q000187:drug effects; D000596:Amino Acids / Q000008:administration & dosage / Q000097:blood; D000704:Analysis of Variance; D000818:Animals; D001522:Behavior, Animal; D002241:Carbohydrates / Q000008:administration & dosage; D045424:Complex Mixtures / Q000008:administration & dosage*; D004192:Discrimination, Psychological / Q000187:drug effects; D004924:Escape Reaction / Q000187:drug effects; D005106:Exploratory Behavior / Q000187:drug effects; D005780:Gelatin / Q000008:administration & dosage*; D007858:Learning / Q000187:drug effects / Q000502:physiology*; D008297:Male; D008568:Memory / Q000187:drug effects / Q000502:physiology*; D011897:Random Allocation; D051381:Rats; D017208:Rats, Wistar; D013037:Spatial Behavior / Q000187:drug effects / Q000502:physiology*; D013550:Swimming; D013997:Time Factors; D014364:Tryptophan / Q000097:blood / Q000172:deficiency* / Q000378:metabolism
D000596:Amino Acids; D002241:Carbohydrates; D045424:Complex Mixtures; D014364:Tryptophan; D005780:Gelatin