Peripheral markers of serotonergic and noradrenergic function in post-pubertal, Caucasian males with autistic disorder

Some studies have suggested that disorders in the peripheral\ and central m etabolism of serotonin(5-HT) and noradrenaline may play a role in the patho physiology of autistic disorder. This study examines serotonergic and norad renergic markers in a study group of 13 males, post-pubertal, caucasian aut istic patients (age 112-18 y; I.Q. > 55) and 13 matched volunteers. [H-3]-p aroxetine binding Kd values were significantly higher in patients with auti sm than in healthy volunteers. Plasma concentrations of tryptophan, the pre cursor of 5-HT, were significantly lower in autistic patients than in healt hy volunteers. There were no significant differences between autistic and n ormal children in the serum concentrations of 5-HT, or the 24-hr urinary ex cretion of 5-hydroxy-indoleacetic acid (5-HIAA), adrenaline, noradrenaline, and dopamine. There were no significant differences in [H-3]-rauwolscine b inding Bmax or Kd values, or in the serum concentrations of tyrosine, the p recursor of noradrenaline, between both study groups. There were highly sig nificant positive correlations between age and 24-hr urinary excretion of 5 -HIAA and serum tryptophan. The results suggest that: 1) serotonergic distu rbances, such as defects in the 5-HT transporter system and lowered plasma tryptophan, may play a role in the pathophysiology of autism; 2) autism is not associated with alterations in the noradrenergic system; and 3) the met abolism of serotonin in humans undergoes significant changes between the ag es of 12 and 18 years. [Neuropsychopharmacology 22:275-283, 2000] (C) 2000 American College of Neuropsychopharmacology. Published by Elsevier Science Inc.