The role of glia in the neuroendocrine hypothalamus: possible implications in hormone secretion.

Recent evidence indicates that glia may play a significant role in the link between the endocrine and nervous systems. Gonadal steroids modulate astroglia morphology, differentiation and gene expression in different brain areas. Hormonal effects on glia may have important consequences for neuronal development, metabolism and activity, for the formation and plasticity of synaptic connections, and for the modulation of hypothalamic hormone release. Perinatal and adult testosterone levels modulate the expression of the specific astroglia cytoskeletal marker glial fibrillary acidic protein in the arcuate nucleus of the rat hypothalamus. These changes parallel hormonal effects on the expression of growth hormone-releasing hormone (GHRH) and the number of GHRH neurones in the arcuate nucleus. The effects of testosterone and its metabolite oestradiol on hypothalamic neurones may be dependent on the release by hypothalamic astroglia of insulin-like growth factor I, a molecule involved in the control of growth hormone secretion.