Platelet serotonin transporter in children and adolescents with obsessive-compulsive disorder or Tourette's syndrome

Previous studies of serotonin transporter protein (5HTPR) indexed in platelets by H-3-imipramine demonstrate reduction in children with comorbid obsessive-compulsive disorder (OCD) and Tourette's syndrome (TS). Objective: To use the 5HTPR selective ligand H-3-paroxetine and homogeneous diagnostic groups to reevaluate these findings. Method: Platelet kinetic binding parameters were evaluated using standard techniques from medication-free child and adolescent patients with OCD (n = 18), with TS (n = 10), and normal controls (n = 19). Results: Baseline binding capacity (B-max) was significantly reduced in patients with OCD (1,342 +/- 952 fmol/mg protein; p <.01) compared with normal controls (2,486 +/- 1309 fmol/mg) and TS patients (2,420 +/- 1,069 fmol/mg; p <.05). Among OCD patients who were subsequently treated on an open-label basis with selective serotonin reuptake inhibitor (SSRI), B-max values at baseline differentiated between responders (1,718 +/- 1,041 fmol/mg) and nonresponders (802 +/- 713 fmol/mg protein; p <.05). Response to SSRI was greatest in patients with a positive family history of OCD. Among responders (n = 10), baseline Yale-Brown Obsessive Compulsive Scale and B-max were positively correlated (r=.76, p =.01), as was Clinical Global Impression (r=.67, p=.03). Conclusions: Platelet 5HTPR capacity (B-max) is reduced in children and adolescents with OCD, but not in those with TS. 5HTPR may be an indirect measure of basal serotonergic tone.