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

UNLABELLED: Previous studies of serotonin transporter protein (5HTPR) indexed in platelets by 3H-imipramine demonstrate reduction in children with comorbid obsessive-compulsive disorder (OCD) and Tourette's syndrome (TS).

OBJECTIVE: To use the 5HTPR selective ligand 3H-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 (Bmax) 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), Bmax 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 Bmax were positively correlated (r = .76, p = .01), as was Clinical Global Impression (r = .67, p = .03).

CONCLUSIONS: Platelet 5HTPR capacity (Bmax) is reduced in children and adolescents with OCD, but not in those with TS. 5HTPR may be an indirect measure of basal serotonergic tone.