Diminished serotonergic functioning in hostile children with ADHD: tryptophan depletion increases behavioural inhibition.
BACKGROUND
Serotonergic (5-HT) functioning has been shown to account for a variety of behavioural characteristics, in particular aggressive and impulsive behaviour. This study explored the effects of rapid tryptophan depletion (RTD) and the ensuing reduction of brain 5-HT synthesis on behavioural inhibition in passive avoidance learning assessed in a computerized go/no-go task.


METHODS
22 male patients with an ICD-10 diagnosis of ADHD were administered RTD within an amino acid drink lacking tryptophan, the natural precursor of 5-HT, thus lowering the central nervous 5-HT synthesis rate in a placebo-controlled double-blind within-subject crossover-design. 4 hours after RTD/placebo intake the patients were subjected to a go/no-go task for assessment of behavioural inhibition.


RESULTS
Highly hostile aggressive patients showed increased inhibition errors under RTD compared to placebo. Low hostile aggressive patients showed lower rates of inhibition errors and thus better performance under RTD compared to placebo.


CONCLUSIONS
The data suggest that in ADHD levels of trait-aggressive characteristics influence the susceptibility to changed behavioural inhibition after an acute 5-HT dysfunction. The detected influence of 5-HT could also be relevant as regards behavioural inhibition being subject to a developmental change in 5-HT functioning.
Zepf
F D
FD
Department of Child and Adolescent Psychiatry and Psychotherapy, JW Goethe University of Frankfurt am Main, Frankfurt am Main, Germany. F.Zepf@med.uni-frankfurt.de
Holtmann
M
M
Stadler
C
C
Demisch
L
L
Schmitt
M
M
Wöckel
L
L
Poustka
F
F
D000374:Aggression / Q000523:psychology; D001289:Attention Deficit Disorder with Hyperactivity / Q000097:blood* / Q000188:drug therapy / Q000523:psychology*; D000697:Central Nervous System Stimulants / Q000627:therapeutic use; D002648:Child; D018592:Cross-Over Studies; D004311:Double-Blind Method; D006791:Hostility; D006801:Humans; D007266:Inhibition, Psychological; D016014:Linear Models; D008297:Male; D008774:Methylphenidate / Q000627:therapeutic use; D009483:Neuropsychological Tests; D011569:Psychiatric Status Rating Scales; D011594:Psychometrics; D012701:Serotonin / Q000097:blood*; D014364:Tryptophan / Q000172:deficiency*
D000697:Central Nervous System Stimulants; D008774:Methylphenidate; D012701:Serotonin; D014364:Tryptophan