Notch signalling is a conserved mechanism involved in direct cell-to-cell communication. In neurons, the inhibition of Notch signalling promotes neuronal dif¬ferentiation124. Notch upregulates the expression of the transcription factor Hairy and enhancer of Split 1 (HES1), which represses the transcription of the neuritogenic fac¬tor neurogenin 3 (NGN3; also known as NEUROG3)124. Recent studies have shown that oestradiol inhibits Notch signalling in primary neurons, decreasing the expres¬sion of HES1 and therefore increasing the expression of NGN3 and neuritogenesis38,124. The oestrogenic regula¬tion of Notch signalling and NGN3 expression is medi-ated by GPER and the activation of the PI3K–AKT signalling pathway38,124 (FIG. 4). The regulation of Notch signalling in neurons may be involved in the regen¬erative actions of the hormone by acting to promote neuritic growth.