Voltage-clamp experiments are routinely used to characterize voltage-gated channels and synaptic currents. Effective clamping is spatially limited by intracellular resistance, however, and it usually cannot be maintained across cellular compartments. This is especially problematic for investigations of somatic voltage-gated sodium channels, because ineffective clamping of the axon allows spike ...

Neurons in vertebrate central nervous systems initiate and conduct sodium action potentials in distinct subcellular compartments that differ architecturally and electrically. Here, we report several unanticipated passive and active properties of the cerebellar granule cell's unmyelinated axon. Whereas spike initiation at the axon initial segment relies on sodium channel (Nav)-associated fibrobl...

Tetrodotoxin (TTX)-sensitive sodium channels carry large transient currents during action potentials and also "persistent" sodium current, a noninactivating TTX-sensitive current present at subthreshold voltages. We examined gating of subthreshold sodium current in dissociated cerebellar Purkinje neurons and hippocampal CA1 neurons, studied at 37°C with near-physiological ionic conditions. Unex...

The estimation and detection of stimuli by sensory neurons is affected by factors that govern a transition from tonic to burst mode and the frequency characteristics of burst output. Pyramidal cells in the electrosensory lobe of weakly electric fish generate spike bursts for the purpose of stimulus detection. Spike bursts are generated during repetitive discharge when a frequency-dependent broa...

We studied the peripheral motor axons of the two pyloric dilator (PD) neurons of the stomatogastric ganglion in the lobster, Homarus americanus. Intracellular recordings from the motor nerve showed both fast and slow voltage- and activity-dependent dynamics. During rhythmic bursts, the PD axons displayed changes in spike amplitude and duration. Pharmacological experiments and the voltage depend...

Axons have traditionally been viewed as highly faithful transmitters of action potentials. Recently, however, experimental evidence has accumulated to support the idea that under some circumstances axonal propagation may fail. Cerebellar Purkinje neurons fire highfrequency simple spikes, as well as bursts of spikes in response to climbing fiber activation (the "complex spike"). Here we have vis...

Neostriatal cholinergic interneurons produce spontaneous tonic firing in the absence of synaptic input. Perforated patch recording and whole-cell recording combined with calcium imaging were used in vitro to identify the intrinsic membrane properties underlying endogenous excitability. Spontaneous firing was driven by the combined action of a sodium current and the hyperpolarization-activated c...

TO THE EDITOR: Although the authors reported interesting findings (Boinagrov et al. 2012), well-known facts such as “the axon is the most excitable part of a neuron” (Nowak and Bullier 1998) or “axonal sodium-channel bands shape the response to electric stimulation in retinal ganglion cells” (Fried et al. 2009) cannot be shown using their presented simple spherical neuron model. Therefore, I re...

Neurons of the subthalamic nucleus (STN) are spontaneously active. By voltage clamping dissociated rat STN neurons with their own firing patterns, we found that pacemaking is driven by two kinds of subthreshold sodium current: a steady-state "persistent" sodium current and a dynamic "resurgent" sodium current, which promotes rapid firing by flowing immediately after a spike. These currents are ...

Yang and Seamans (J. Neurosci. 16 (5) (1996) 1922}1935) have recently shown that pyramidal cells in rat prefrontal cortex respond to a brief current injection with a plateau potential that is mediated by slowly inactivating voltage-dependent sodium currents. They also report that dopamine receptor activation increases plateau duration and shifts its activation to more negative potentials. We mo...