5-HT1A receptor and 5-HTT binding during the menstrual cycle in healthy women examined with [11C] WAY100635 and [11C] MADAM PET

The aim of the present study was to explore the effects of the menstrual cycle phases on 5-HT1A receptor and 5-HTT binding potentials (BPs) in healthy women by using positron emission tomography (PET). Women were investigated in the follicular and luteal phase of the menstrual cycle with radioligands [11C]WAY10035 (n = 13) and [11C]MADAM (n = 8) to study 5-HT1A and 5-HTT BPs. The BPs values were quantified using the simplified reference tissue model. The phases of the menstrual cycle were characterized by transvaginal ultrasound (TSV) and plasma levels of hormones estradiol (E2), progesterone (P4), follicle stimulating hormone (FSH) and luteinizing hormone (LH).The 5-HT1A receptor and 5-HTT BPs did not significantly differ between follicular and luteal phases in any of the investigated regions. There were no significant correlations between the change in E2 or P4 values with the change in 5-HT1A receptor or 5-HTT BPs. The results provide principally a new in vivo finding in human female biology, suggesting the absence of influence of menstrual cycle phase on 5-HT1A receptors or 5-HTT. The finding however does not preclude that gonadal hormones differentially influence central serotonin system inwomen and men, which might contribute to gender differences in serotonin-associated disorders.