Single wavelength calcium imaging of dorsal root ganglia growth cones in response to a microgradient of brain derived neurotrophic factor (BDNF). (A) Control morphant growth cone showing robust calcium flux in response to a BDNF gradient. (B) Homer1 morphant growth cone showing dramatic reduction of BDNF-induced calcium release. Frame interval is 18 s. The BDNF microgradient was established at the 'BDNF' frame. Frames marked with asterisks indicate spontaneous calcium transients.