This article is a study of the fast Na current during action potentials. We have investigated the outward Na current (Mazzanti, M., and L.J. DeFelice. 1987. Biophys. J. 52:95-100) in more detail, and we have asked whether it goes through the same channels associated with the rapid depolarization phase of action potentials. We address the question by patch clamping single, spontaneously beating,...

The electromechanical responses to isoprenaline and a high calcium medium on cardiac muscles from nonhibernating and hibernating chipmunks were studied in the presence and the absence of ryanodine. In nonhibernating animal preparations, isoprenaline (5 X 10(-8) M) caused a marked positive inotropic effect with an increase in the amplitude of the action potential plateau and augmented the slow a...

Somatic spiking is known to regulate dendritic signaling and associative synaptic plasticity in many types of large neurons, but it is unclear whether somatic action potentials play similar roles in small neurons. Here we ask whether somatic action potentials can also influence dendritic signaling in an electrically compact neuron, the cerebellar stellate cell (SC). Experiments were conducted i...

Multiunit neural activity occurs often in electrophysiological studies when utilizing extracellular electrodes. In order to estimate the activity of the individual neurons each action potential in the recording must be classified to its neuron of origin. This paper compares the accuracy of two traditional methods of action potential classification--template matching and principal components--ag...

To investigate the possibility of transmural recording of repolarization through the ventricular wall, KCl monophasic action potential (MAP) electrodes positioned along plunge needles were developed and tested. The MAP electrode consists of a silver wire surrounded by agarose gel containing KCl, which slowly eluted into the adjacent tissue to depolarize it. In six dogs, a plunge needle containi...

(1.1) Cm ∂V ∂t = 1 Ra ∂2V ∂x2 − Iion(V, t)− Istim(t), where Ra and Cm are the axial resistance and membrane capacitance, Iion represents the total ionic current, and Istim(t) is an applied stimulus current which instigates an action potential. The source term Iion is usually specified by some Hodgkin-Huxley type ionic model. In our simulations, we use the Luo-Rudy phase I (1991) model, one of t...

Action potentials reflect the concerted activity of all electrogenic constituents in the plasma membrane during the excitation of a cell. Therefore, the action potential is an integrated read out and a promising parameter to detect electrophysiological failures or modifications thereof in diagnosis as well as in drug screens. Cellular action potentials can be recorded by optical approaches. To ...

A fundamental problem in developing therapeutic interventions for uterine dysfunction is that the electrical profile of the myometrium, and how it changes in physiological, let alone pathophysiological, situations is unknown. Excitation-contraction coupling of the myometrium is a central component of healthy functioning of the uterus. Even though proper function of this smooth muscle is fundame...

Neurons encode information and communicate via action potentials, which are generated following the summation of synaptic events. It is commonly assumed that action potentials reset the membrane potential completely, allowing another round of synaptic integration to begin. We show here that the conductances underlying the action potential act instead as a variable reset of synaptic integration....

The nonlinear dynamics of cardiac action potentials is explained via simple model equations describing the membrane potential and the inward and outward currents through the membrane. The equations approximate ionic models, yet are expressed as polynomial functions, and robustly capture the phase-space dynamics of action potentials.