SEROTONIN 5-HT2A RECEPTOR-BINDING IN PLATELETS FROM HEALTHY-SUBJECTS AS STUDIED BY [H-3] LYSERGIC-ACID DIETHYLAMIDE ([H-3]-LSD) - INTRA-INDIVIDUAL AND INTERINDIVIDUAL VARIABILITY

In studies on platelet 5-HT2A receptor binding in patients with neurop sychiatric disorders, there has been a marked variability and a consid erable overlap of values between patients and controls. The causes of the large variability in 5-HT2A receptor parameters is still unsettled . In the present study, we have quantified the intra- and interindivid ual variability of platelet 5-HT2A receptor binding in 112 healthy sub jects and explored factors that may influence 5-HT2A receptor binding, using [H-3]-lysergic acid diethylamide as radioligand. Age, gender, b lood pressure, and metabolic capacity of the liver enzymes CYP2D6 and CYP2C19 did not influence B-max and K-d values. Body weight and body m ass index (BMI) showed a negative correlation with K-d (p = .04 and .0 3, respectively), but not with B-max. B-max was significantly lower in the light half of the year than in the dark half of the year (p = .00 1), and K-d was significantly lower in the fall than in the summer and winter (p < .001). In females, there was a significant increase in B- max from week 1 to week 2 of the menstrual cycle (p = .03). Females ta king contraceptive pills had significantly higher K-d than drug-free f emales in weeks 1 and 4 of the menstrual cycle (p = .04). This study s hows that a number of factors should be taken into account when using platelet 5-HT2A receptor binding in studies of neuropsychiatric disord ers. (C) 1997 American College of Neuropsychopharmacology.