In summary, the data examined in this chapter indicate that neurosteroids and hormonal steroids affect brain function not only by direct effects on neurons, but also that glial cells may participate in the effects of neuroactive steroids by modulating neuronal responses under physiological and pathological conditions. Gonadal steroids and neurosteroids promote astroglia plasticity in several areas of the CNS, including the hypothalamus, the striatum, and the hippocampus, and modulate astroglia proliferation and the formation of reactive astroglia after brain injury. Under physiological conditions, the effects of steroids on astroglia may be involved in the sexual differentiation of synaptic connectivity and in synaptic plastic events during adult life. Recent evidence indicates that the effects of neuroactive steroids in brain may be in part mediated by growth factors, such as IGF-I. Astroglia also may play a crucial role by regulating the availability of such factors to neurons.

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