NGF and overactive bladder: Along with this line of research, the present study examines 1) whether endogenous NGF has a role in CGRP expression in the DRG and in inducing bladder overactivity caused by cystitis; 2) whether cystitis-induced CGRP involves NGF retrograde signaling that involves activation of ERK5 and Akt; and 3) the involvement of CREB in NGF signaling.