Action des stéroïdes sur le cerveau

Abstract

Brain is a target organ for steroids produced by pheripheral glands, such estradiol, as well as for those synthesized locally by nerve tissue (neurosteroids, name introduced by E.E. BAULIEU). Steroids are able to affect neuronal and glial activity. Some steroids regulate synaptic function, and therefore brain function, by having rapid effects on neurotransmitter receptors such as GABAA or nicotinic receptors. Hormonal steroids have genomic actions as well, consecutive to the activation of their intranuclear receptors; transcription factors that regulate the expression of specific genes. By activating their receptors, estradiol regu- lates neuronal survival and differentiation as well as synaptic plasticity in the hypothalamus. Recently it has been shown that some brain actions of estradiol are dependent on the activation of growth factor signaling. For instance, a co-activation of estradiol and IGF-I receptors is necessary for the manifestation of the trophic and plastic effects of the hormone on hypothalamic neurons.