We investigated the ionic interactions responsible for the characteristic nonrepetitive spike activity of amacrine cells. First we measured 4 pharmacologically separable ionic components: a voltage-gated, transient inward sodium current, a voltage-gated, sustained inward calcium current, a calcium-gated, sustained outward potassium current, and a voltage-gated, transient outward potassium curre...

Pump activity is a homeostatic mechanism that maintains ionic gradients. Here we examined whether the slow reduction in excitability induced by sodium-pump activity that has been seen in many neuronal types is also involved in neuronal coding. We took intracellular recordings from a spike-bursting sensory neuron in the leech Hirudo medicinalis in response to naturalistic tactile stimuli with di...

Thin, unmyelinated axons densely populate the mammalian hippocampus and cortex. However, the location and dynamics of spike initiation in thin axons remain unclear. We investigated basic properties of spike initiation and propagation in CA3 neurons of juvenile rat hippocampus. Sodium channel alpha subunit distribution and local applications of tetrodotoxin demonstrate that the site of first thr...

The principal computational operation of neurones is the transformation of synaptic inputs into spike train outputs. The probability of spike occurrence in neurones is determined by the time course and magnitude of the total current reaching the spike initiation zone. The features of this current that are most effective in evoking spikes can be determined by injecting a Gaussian current wavefor...

Classical accommodation is a form of spike frequency adaptation in neurons whereby excitatory drive results in action potential output of gradually decreasing frequency. Here we describe an essential molecular component underlying classical accommodation in juvenile mouse hippocampal CA1 pyramidal neurons. A-type isoforms of fibroblast growth factor homologous factors (FHFs) bound to axosomatic...

A computational model was developed to evaluate the influence of the calcium-dependent potassium conductance (gKCa), the calcium concentration in soma (varying the velocity of calcium extrusion velext and the calcium conductances in soma – gCaN and gCaP), the inclusion of a slow inactivation state variable in soma's fast sodium conductance and the conductance of the persistent sodium current in...

In vivo neocortical neurons fire apparently random trains of action potentials in response to sensory stimuli. Does this randomness represent a signal or noise around a mean firing rate? Here we use the timing of action potential trains recorded in vivo to explore the dendritic consequences of physiological patterns of action potential firing in neocortical pyramidal neurons in vitro. We find t...

Persistent sodium channel activity modulates neuronal gain in a neurotransmitter-dependent fashion. Previous studies have suggested that persistent and spike-related sodium channel activities are mediated by separate species. In this issue of Neuron, Taddese and Bean (2002) show that a single channel population is sufficient to explain both gating behaviors. A simple allosteric model is provide...