A "slow" inward current (Is) has been identified in ventricular muscle and Purkinje fibers of several mammalian species. The two-microelectrode voltage clamp technique is used to examine some of the relationships between Is and contraction of the sheep cardiac Purkinje fiber. "Tails" of inward current occurring on repolarization and extrapolation of Is recovery each show that the Is system may ...

Without synaptic input, Purkinje neurons can spontaneously fire in a repeating trimodal pattern that consists of tonic spiking, bursting and quiescence. Climbing fiber input (CF) switches Purkinje neurons out of the trimodal firing pattern and toggles them between a tonic firing and a quiescent state, while setting the gain of their response to Parallel Fiber (PF) input. The basis to this trans...

In an investigation into the transformation of mossy ber input to Purkinje cell output in the cerebellar cortex, we have developed a network model including a sophisticated compartmental model of the Purkinje cell. Analysis and simulations demonstrated the need to include a large number of parallel bers (244,000) to obtain realistic Purkinje cell ring patterns for random mossy ber input. Using ...

Although the antiarrhythmic aspect of amiodarone has been extensively studied, its effects on His-Purkinje system conduction and refractoriness have not been systematically investigated in human beings. In 24 patients, anterograde His-Purkinje system conduction (HV intervals) and variables of His-Purkinje system refractoriness using the ventricular extrastimulus (V2) technique were analyzed bef...

Papillary muscle-false tendon tissue preparations isolated from dog hearts were perfused with Tyrode's solution containing propranolol in concentrations ranging from 0.1 to 20.0 mg/liter. Transmembrane action potentials of both ventricular muscle fibers and Purkinje fibers were recorded. With sufficient concentration of drug, the velocity of the upstroke and the overshoot of both fiber types de...

Tottering mouse is an ataxic mutant that carries a mutation in a gene encoding for the apha1A subunit of P/Q-type Ca2+ channel (Cav2.1). This study revisited to examine whether a Purkinje cell loss occurred in the cerebellum of tottering mice. In tottering mice, Calbindin D-28k negative gaps were apparent in the vermis but not in the hemisphere. Calbindin D-28k immunofluorescence with DAPI stai...

Previous studies have implicated the role of Purkinje cells in motor learning and the underlying mechanisms have also been identified in great detail during the last decades. Here we report that cyclin-dependent kinase 5 (Cdk5)/p35 in Purkinje cell also contributes to synaptic plasticity. We previously showed that p35(-/-) (p35 KO) mice exhibited a subtle abnormality in brain structure and impa...

Purkinje neurons play an important role in cerebellar computation since their axons are the only projection from the cerebellar cortex to deeper cerebellar structures. They have complex internal dynamics, which allow them to fire spontaneously, display bistability, and also to be involved in network phenomena such as high frequency oscillations and travelling waves. Purkinje cells exhibit type ...

Recent studies have demonstrated that the membrane potential of Purkinje cells is bi-stable and that this phenomenon underlies bi-modal simple spike firing. Membrane potential alternates between a depolarized state, that is associated with spontaneous simple spike firing (up state), and a quiescent hyperpolarized state (down state). A controversy has emerged regarding the relevance of bi-stabil...

Cerebellar Purkinje cells display complex intrinsic dynamics. They fire spontaneously, exhibit bistability, and via mutual network interactions are involved in the generation of high frequency oscillations and travelling waves of activity. To probe the dynamical properties of Purkinje cells we measured their phase response curves (PRCs). PRCs quantify the change in spike phase caused by a stimu...