Figure 6

Spontaneous calcium transients and growth cone turning are sensitive to blockage of store-operated channels. (A) Individual control morphant growth cones exhibited sparse spontaneous calcium transients, occurring at a rate of approximately one transient per three minutes. (B) Homer1 morphant growth cones exhibited significantly greater frequency, at a rate of at least one spontaneous transient per minute. (C) A trace from a single Homer1 morphant growth cone showed a decrease in spontaneous calcium transient frequency in the presence of bath applied SKF-96365. (D) Quantification of spontaneous calcium transient frequencies in Homer1 morphant growth cones. Removing calcium from the media (Ca free) or bath application of La³⁺ (La) or SKF-96365 (SKF) reduced spontaneous transient frequencies in Homer1 morphant growth cones to control (ctrl) levels. Bath application of a voltage-gated calcium channel (VGCC) inhibitor cocktail or nifedipine alone had little effect on the frequency of spontaneous calcium transients in Homer1 morphant growth cones. (E) Calcium-dependent brain derived neurotrophic factor (BDNF)-induced turning is mediated through store-operated channels. BDNF attraction was abolished when TRPC channels were inactivated with bath application of SKF-96365 or La³⁺. Inhibition of VGCCs with nifedipine or ω-conotoxin-MVIIC had no effect on control and Homer1 morphant growth cone turning. (F) Inhibition of store-operated channels did not alter axon extension rates. Error bars indicate standard error of the mean. Cocktail = nifedipine, ω-conotoxin-MVIIC plus Ni⁺⁺. The scale bar in (C) applies also to (A, B).