Dataset Information

Evoked membrane potential change in rat optic nerve fiber: computer simulation.

ABSTRACT: The optic nerve is a key component regarding research on visual prosthesis. Previous pharmacological and electrical studies has pinned down the main features of the mechanisms underlying the nerve impulse in the rat optic nerve, and this work proposed a mathematical model to simulate these phenomena.The main active nodal channels: fast Na+, persistent Na+, slow K+ and a fast repolarizing K+ (A-current) were added on a double layer representation of the axon. A simplified representation of K+ accumulation and clearance in the vicinity of the Ranvier node was integrated in this model.The model was able to generate the following features. In the presence of 4-aminopyridine (4-AP), spike duration increased and a depolarizing afterpotential (DAP) appeared. In the presence of 4-AP and tetraethylammonium (TEA), the DAP was followed by a hyperpolarizing afterpotential (AHP) and the amplitude of this AHP increased with the frequency of the stimulation. In normal conditions (no drugs): DAP and AHP were absent after a single action potential (AP) and a short train of AP; there was a relative refractoriness in amplitude lasting for 30 ms after an AP; an early AHP was revealed by a continuous depolarizing current; and there was a partial spike adaptation for a long current step stimulus.The model successfully reproduced previous experiments results including long-lasting stimulation experiment, which is known to modify nerve physiological parameter values and is a key issue for visual prosthesis research.

SUBMITTER: Cazenave-Loustalet V

PROVIDER: S-EPMC5550649 | biostudies-other | 2007 Nov

REPOSITORIES: biostudies-other

ACCESS DATA

Similar Datasets

Project description:SIGNIFICANCE:This study resulted in the identification of an optic nerve head (ONH) feature associated with tilted optic discs, which might potentially contribute to ONH pathologies. Knowledge of such findings will enhance clinical insights and drive future opportunities to understand disease processes related to tilted optic discs. PURPOSE:The aim of this study was to identify novel retinal nerve fiber layer (RNFL) anomalies by evaluating tilted optic discs using optical coherence tomography. An observed retinal nerve fiber protrusion was further investigated for association with other morphological or functional parameters. METHODS:A retrospective review of 400 randomly selected adult patients with ONH examinations was conducted in a referral-only, diagnostic imaging center. After excluding other ONH pathologies, 215 patients were enrolled and evaluated for optic disc tilt and/or torsion. Gross anatomical ONH features, including size and rim or parapapillary region elevation, were assessed with stereoscopic fundus photography. Optical coherence tomography provided detailed morphological information of individual retinal layers. Statistical analysis was applied to identify significant changes between individual patient cohorts. RESULTS:A dome-shaped hyperreflective RNFL bulge, protruding into the neurosensory retina at the optic disc margins, was identified in 17 eyes with tilted optic discs. Available follow-up data were inconclusive regarding natural changes with this ONH feature. This RNFL herniation was significantly correlated with smaller than average optic disc size (P = .005), congenital disc tilt (P < .0001), and areas of rim or parapapillary elevation (P < .0001). CONCLUSIONS:This study reports an RNFL protrusion associated with tilted optic discs, which has not previously been assessed as an independent ONH structure. The feature is predominantly related to congenital crowded, small optic discs and variable between patients. This study is an important first step to elucidate diagnostic capabilities of tilted disc morphological changes and understanding associated functional deficits.

Dataset Information

Evoked membrane potential change in rat optic nerve fiber: computer simulation.

Similar Datasets

OmicsDI is part of the ELIXIR infrastructure

Tweets