Oestrogen modulation of noradrenaline neurotransmission.

Noradrenaline (NA) exerts an important neuromodulatory role within diverse neuronal networks and is also likely to be a target for oestrogen in the brain. Distinct, highly organized sub-populations of brainstem NA neurons express oestrogen receptors (ERs) and some of these display species differences. A number of genes expressed by NA neurons, ranging from transcription factors to co-released neuropeptides, are influenced by oestrogen and may have roles in the predominant enhancement in NA activity in response to oestrogen. The effects of oestrogen on genes involved directly in NA biosynthesis are less clear, although promoter transgenic work suggests oestrogen to have a powerful influence upon tyrosine hydroxylase gene transcription. In addition to direct actions on NA neurons, evidence suggests that oestrogen also regulates adrenergic receptor expression and function within the ER-rich hypothalamus as well as the cerebral cortex. Together, these investigations point to a multifaceted pre- and postsynaptic regulation of NA transmission by oestrogen. While the hypothalamic neuronal networks controlling reproduction remain the principal site of investigation of oestrogen regulated NA transmission, the role of oestrogen and NA and their potential interactions in cortical functioning are becoming of equal interest.