title: The influence of daylight exposure on platelet 5-HT levels in patients with major depression and schizophrenia.
abstract: Platelet serotonin (5-HT) can be used as a limited, peripheral model for the central 5-HT synaptosomes. Altered platelet 5-HT concentrations have been associated with psychiatric disorders like depression and schizophrenia. The aim of the present study was to compare platelet 5-HT concentrations during long, medium and short period of natural daylight exposure in a large number of medication-free male and female schizophrenic and depressed patients and sex-matched healthy controls. Platelet 5-HT concentration was determined spectrofluorimetrically in 240 (97 female, 143 male) schizophrenic and 258 (153 female, 105 male) nonpsychotic, nonsuicidal depressed medication-free patients and 328 (149 women, 179 men) healthy subjects during periods with short (<12), long (>12) and medium (average 12) hours of the natural daylight. Platelet 5-HT concentration was significantly lower in women compared to men in all groups. Healthy male subjects had significantly higher (p=0.011) platelet 5-HT concentrations during long compared to medium period. There were no significant differences (p>0.05) in platelet 5-HT concentration between different periods in healthy women. The significant increase in platelet 5-HT values were found in female (p=0.01) and male (p=0.029) depressed patients during long compared to short period. There were no significant associations between platelet 5-HT concentrations and different periods in both male and female schizophrenic patients. The results indicate the sex-related differences in the serotonergic system. The alterations of platelet 5-HT concentrations, observed across period with different durations of daylight exposure, point to a direct or indirect effect of light on peripheral 5-HT system that could be related to different sensitivity of the pineal gland to light and/or melatonin influence on 5-HT metabolism.
authors.affiliation: Psychiatric Clinic, Clinical Hospital Centre Rijeka, Rijeka, Croatia.
authors.forename: Dulijano
authors.initials: D
authors.lastname: Ljubicić
authors.forename: Tamara
authors.initials: T
authors.lastname: Stipcević
authors.forename: Nela
authors.initials: N
authors.lastname: Pivac
authors.forename: Miro
authors.initials: M
authors.lastname: Jakovljević
authors.forename: Dorotea
authors.initials: D
authors.lastname: Mück-Seler
mesh_terms: D000328:Adult; D001792:Blood Platelets / Q000737:chemistry* / Q000528:radiation effects; D003866:Depressive Disorder / Q000097:blood*; D005260:Female; D006801:Humans; D008027:Light; D008297:Male; D008875:Middle Aged; D012559:Schizophrenia / Q000097:blood*; D012621:Seasons; D012701:Serotonin / Q000097:blood* / Q000528:radiation effects; D012737:Sex Factors
chemical_list: D012701:Serotonin