Ovarian hormones and effects in the brain studies of neurosteroid sensitivity, serotonin transporter and serotonin2A receptor binding in reproductive and postmenopausal women

Sammanfattning: Background: Estrogen has been reported to enhance well-being and quality of life during the climacteric phase. In women with an intact uterus estrogen treatment is always combined with progestins in order to protect the endometrium from hyperplasia and malignancies. However, in certain women the addition of progestins causes cyclicity in negative mood symptoms and physical symptoms similar to those encountered during ovulatory cycles in women with premenstrual dysphoric disorder (PMDD). The ovarian hormones estradiol and progesterone have profound effects on a number of neurotransmitter systems in the brain, such as the gamma aminobutyric acid (GABA) system and the serotonergic system. Progesterone metabolites, such as allopregnanolone and pregnanolone (also referred to as neurosteroids) modify the GABAA receptor in the central nervous system (CNS) and enhance GABAergic inhibitory transmission. Neurosteroid sensitivity in human studies can be studied by saccadic eye movement measurements using pharmacodynamic challenges with pregnanolone. Altered neurosteroid sensitivity has been suggested as a possible contributory factor to the progesterone/progestin-induced adverse mood effects of hormone replacement therapy (HRT). There is also evidence of estrogen treatment affecting the serotonergic system in postmenopausal women, although progestin addition has been less well studied.Aims and method: The aim was to investigate whether the negative mood symptoms experienced during the progestin or progesterone phase of HRT were associated with changes in neurosteroid sensitivity, or changes in platelet serotonin uptake site (transporter) and serotonin2A (5-HT2A) receptor binding. The intention was also to investigate whether hormonal changes during the normal menstrual cycle affect these peripheral serotonergic parameters. Postmenopausal women with climacteric symptoms were given HRT in two randomized, double-blinded, placebo-controlled crossover studies. The women received 2 mg estradiol (E2) continuously during 28- day cycles. Synthetic progestins or natural progesterone were added sequentially during the last 14 days, and compared to a placebo addition. Before treatment, as well as during the last week of each treatment cycle the pharmacodynamic response to pregnanolone was assessed using saccadic eye movement measurements. Throughout the studies daily symptom ratings were made. In the study regarding synthetic progestins, platelet serotonin transporter and 5-HT2A receptor binding were assayed before entering the study, as well as during the last week of each treatment cycle. In the study on reproductive women, blood samples were collected for analysis of platelet serotonin transporter and 5-HT2A receptor binding at six different points in time during the menstrual cycle.Results and conclusion: The addition of synthetic progestins to estrogen treatment increased negative mood symptoms and physical symptoms, whereas positive symptoms decreased. The addition of progestins also increased the sensitivity to pregnanolone. The addition of natural progesterone to estrogen treatment increased the sensitivity to pregnanolone. However, in this study the pregnanolone sensitivity was enhanced also during estrogen treatment. Women expressing cyclicity in negative mood symptoms were more sensitive to pregnanolone than women without symptom cyclicity. Thus, it is evident that mood deterioration during HRT is associated with altered neurosteroid sensitivity. Platelet serotonin transporter and 5-HT2A receptor binding did not change during the different treatment conditions in HRT. Thus, we were unable to explain the negative mood changes of HRT by use of these peripheral serotonergic parameters. In the study on reproductive women however, it was clear that the serotonergic variables did change during the menstrual cycle. Binding to the serotonin transporter was higher in the late follicular phase than in the ovulatory, early luteal or mid-luteal phases. Binding to the 5-HT2A receptor was higher in the early follicular phase and the early luteal phase than in the mid-luteal phase. These findings may provide a link between the ovarian steroids, and the GABAergic and serotonergic neurotransmitter systems, which in turn, could explain part of the specific vulnerability that women have for the development of adverse mood effects during HRT, mood and anxiety disorders and for the deterioration of mood so frequently seen during the luteal phase.