**3.6 Other signaling pathways involved in dendritic growth**

Retinoic acid synthesis enzymes and signaling pathway components are expressed in embryonic sympathetic neurons and activation of retinoic acid signaling in embryonic SCG neurons *in vitro* inhibits BMP-7 induced dendritic growth [164]. Similarly, pituitary adenylate cyclase 38(PACAP 38) and vasoactive intestinal peptide (VIP) are released by the preganglionic neurons and in cultured perinatal sympathetic neurons, PACAP38 and VIP decrease the number of dendrites and the total dendritic arbor of BMP-7 treated neurons. This effect is mediated through activation of the PAC1 receptor leading to the phosphorylation and nuclear translocation of cyclic AMP response element binding (CREB) protein, with inhibition of adenylate cyclase activity leading to enhanced dendritic growth [165].
