Figure 2.

Oestrogen is known to affect neurones in the arcuate nucleus, the VMH, the PVN and lateral hypothalamus (LH). Nuclear oestrogen receptors (ERα, ERβ) are expressed in all of these hypothalamic nuclei. Two membrane ER, GPR30 and Gq-mER are also expressed in the hypothalamus. GPR30 is expressed in the PVN and the arcuate nucleus while the Gq-mER is has been functionally identified in arcuate POMC neurones. The Gq-mER rapidly increases the neuronal excitability, and over the long term gene expression, of these anorectic neurones which have multiple projections to the VMH, the PVN and the lateral hypothalamus (LH). These projections (dashed line) potentially synapse on several of the neurones that control feeding behaviour, energy expenditure, etc., and affect these neurones through the α–MSH MC3/4 receptor. Kelly and colleagues have hypothesised that the oestrogenic activation of POMC neurones by the Gq-mER is important for the control of energy homeostasis as evidenced by the effects of the selective Gq-mER agonist, STX, on post-ovariectomy body weight gain. This hypothesis is supported by Polidori & Geary (100) in which the anorectic effects of oestrogen were blocked by antagonists of the MC3/4 receptor infused into the lateral ventricle near the PVN.