The dual action of estrogen hypothesis

Estradiol (E-2) can act in the brain in a relatively fast manner (i.e., seconds to minutes) usually through signaling initiated at the cell membrane. Brain-derived E-2 has thus been considered as another type of neurotransmitter. Recent work found that behaviors indicative of male sexual motivation are activated by estrogenic metabolites of testosterone (T) in a fast manner, while sexual performance (copulatory behavior per se) is regulated by brain E-2 in a slower manner via nucleus-initiated actions. This functional division between these two types of action appears to generalize to other behavioral systems regulated by E-2. We propose the dual action of estrogen hypothesis to explain this functional distinction between these two different modes of action.