The signature conductances underlying the action potential in neurons are transient. However, it is the intervals between impulses dominated by persistent conductances that make up the neural code. Fundamentally and first to be recognised, leak conductances define the resting membrane potential which provides the driving force for voltage signalling and sets the voltage barrier to be overcome for generation of action potentials. A range of conductances contribute to the leak: K+, Na+ and Ca2+ conductances further subdivided by their voltage sensitivity/insensitive and modes of modulation. It is these properties and the expression sites that define the separate functional roles. Surprisingly, the molecular entities behind leak conductances are still partly or completely unknown. The intrinsic response properties of neurons, i.e. the response patterns evoked by external input, is specific for each cell type. Much of the dynamic complexity originates from the interplay of persistent conductances expressed in the soma-dendritic membrane. Characteristically these conductances dominate in the voltage range between the resting membrane potential and the threshold for action potentials. For this reason they are major players in synaptic integration. Not surprising they are also important targets for modulatory synaptic regulation.