Selective oestrogen receptor modulators--current and future brain and behaviour applications.

Selective oestrogen receptor modulators (SERMs) are compounds that act as oestrogen agonists on selected targets while being oestrogen antagonists on others. The main targets of SERMs are oestrogen agonist activity on bone metabolism and several functions of the cardiovascular system, as well as oestrogen antagonism in the breast and uterus. They are indicated for the treatment and/or prevention of breast and endometrial cancer, osteoporosis and coronary heart disease. The extensive documentation of the multiple oestrogen effects on the CNS, greater understanding of the mechanisms of action, and especially the discovery of a second oestrogen receptor with differentiated distribution and mechanisms, have all led the way to the possibility of specific CNS-targeted SERMs. The demonstration that oestrogen selectively improves cognition, delays the appearance of Alzheimer's dementia, improves the feeling of well-being, as well as the response to antidepressant medications, provides targeted CNS indications for SERMs. The CNS effects of the currently marketed SERMs are not sufficiently explored yet. However, in postmenopausal women, tamoxifen and raloxifene probably show the most oestrogen agonist CNS effects. In women of reproductive age, competition with oestrogen probably exists, resulting in antagonist effects. Activity in men is still mostly unknown. It is quite safe to predict that the recent accumulation of knowledge, combined with the large, thirsty anticipated market for these 'designer oestrogens', will lead to clinical trials of CNS-targeted SERMs in the very near future.