Homer signalling operates in a calcium-dependent manner and regulates the operational state of a calcium-calmodulin dependent protein kinase II-calcineurin phosphatase molecular switch. (A, C) Average growth cone turning angles for control (open bars) and Homer (shaded bars) morphant growth cones in response to brain derived neurotrophic factor (BDNF) and Sema-3a gradients following a 20 minute bath application of (A) cyclosporinA (CsA) or (C) KN93 and KN92. (B, D) Axon extension rates were not significantly different amongst control and Homer1 morphants with the same pharmacological treatments. Significant differences from control values are marked as: **P < 0.005; ***P < 0.0005; Mann-Whitney U-test. Error bars indicate standard error of the mean.