Small voltage changes at nerve terminals travel up axons to affect action potential initiation

Nerve terminals are generally considered the destination points for electrical signals, which propagate unidirectionally from the soma to nerve terminals. Here, we demonstrate that small hyperpolarizations or depolarizations (~10 mV), generated under physiological conditions in rat nerve terminals, backpropagate up the axon (~400 – 800 µm), and change the threshold for initiating action potentials and thus firing patterns. These results suggest a novel mechanism for information processing in neurons and neuronal circuits.