Neurotrophic and neuroprotective actions of estrogens and their therapeutic implications

Originally known for its regulation of reproductive functions, estradiol, a lipophilic hormone that can easily cross plasma membranes as well as the b lood-brain barrier maintains brain systems subserving arousal, attention, m ood, and cognition. In addition, both synthetic and natural estrogens exert neurotrophic and neuroprotective effects. There is increasing evidence tha t estrogen actions are mediated by nongenomic as well as direct and indirec t genomic pathways. Although in vitro models have provided the most extensi ve evidence for neurotrophic and neuroprotective actions to date, there are also in vivo studies that support these actions.