Timing and site of nerve growth factor synthesis in developing skin in relation to innervation and expression of the receptor.

We show that nerve growth factor (NGF) synthesis in developing skin begins with sensory innervation and that sensory neurons do not express NGF receptors until their fibres reach their cutaneous targets. Both cutaneous epithelium and mesenchyme synthesize NGF, the concentration of messenger RNA for NGF being higher in the more densely innervated epithelium.