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 modu late astroglia morphology, differentiation and gene expression in diff erent brain areas. Hormonal effects on glia may have important consequ ences for neuronal development, metabolism and activity, for the forma tion 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 hyp othalamus. These changes parallel hormonal effects on the expression o f growth hormone-releasing hormone (GHRH) and the number of GHRH neuro nes in the arcuate nucleus. The effects of testosterone and its metabo lite oestradiol on hypothalamic neurones may be dependent on the relea se by hypothalamic astroglia of insulin-like growth factor I, a molecu le involved in the control of growth hormone secretion.