Search results for "action potential"
showing 10 items of 233 documents
Efficacy of obidoxime in human organophosphorus poisoning: determination by neuromuscular transmission studies.
1995
Six patients with organophosphorus compound intoxications developed an intermediate syndrome (weakness and fasciculations) and obidoxime was given on eight occasions. The efficacy of the acetylcholinesterase (AChE) reactivator was monitored electrophysiologically by neuromuscular transmission studies using single and repetitive nerve stimulation (20 and 50 Hz) and the activity of the serum (butyryl) cholinesterase (ChE). Dramatic electrophysiologic improvement was seen when obidoxime was given early within 12 h in 3 patients, although evidence of AChE inhibition did not subside completely. When administration of obidoxime was delayed 26 h or more after intoxication on five occasions, electr…
Polycyclic Aromatic Hydrocarbons Phenanthrene and Retene Modify the Action Potential via Multiple Ion Currents in Rainbow Trout Oncorhynchus mykiss C…
2019
Polycyclic aromatic hydrocarbons (PAHs) are ubiquitous contaminants in aqueous environments. They affect cardiovascular development and function in fishes. The 3-ring PAH phenanthrene has recently been shown to impair cardiac excitation-contraction coupling by inhibiting Ca2+ and K+ currents in marine warm-water scombrid fishes. To see if similar events take place in a boreal freshwater fish, we studied whether the PAHs phenanthrene and retene (an alkylated phenanthrene) modify the action potential (AP) via effects on Na+ (INa ), Ca2+ (ICaL ), or K+ (IKr , IK1 ) currents in the ventricular myocytes of the rainbow trout (Oncorhynchus mykiss) heart. Electrophysiological characteristics of myo…
Alterations in membrane and firing properties of layer 2/3 pyramidal neurons following focal laser lesions in rat visual cortex.
2013
Focal cortical injuries are well known to cause changes in function and excitability of the surviving cortical areas but the cellular correlates of these physiological alterations are not fully understood. In the present study we employed a well established ex vivo-in vitro model of focal laser lesions in the rat visual cortex and we studied membrane and firing properties of the surviving layer 2/3 pyramidal neurons. Patch-clamp recordings, performed in the first week post-injury, revealed an increased input resistance, a depolarized spike threshold as well as alterations in the firing pattern of neurons in the cortex ipsilateral to the lesion. Notably, the reported lesion-induced alteratio…
Modelling the spatial and temporal constrains of the GABAergic influence on neuronal excitability
2021
GABA (γ-amino butyric acid) is an inhibitory neurotransmitter in the adult brain that can mediate depolarizing responses during development or after neuropathological insults. Under which conditions GABAergic membrane depolarizations are sufficient to impose excitatory effects is hard to predict, as shunting inhibition and GABAergic effects on spatiotemporal filtering of excitatory inputs must be considered. To evaluate at which reversal potential a net excitatory effect was imposed by GABA (EGABAThr), we performed a detailed in-silico study using simple neuronal topologies and distinct spatiotemporal relations between GABAergic and glutamatergic inputs. These simulations revealed for GABAe…
A subset of ventral tegmental area dopamine neurons responds to acute ethanol
2015
The mechanisms by which alcohol drinking promotes addiction in humans and self-administration in rodents remain obscure, but it is well known that alcohol can enhance dopamine (DA) neurotransmission from neurons of the ventral tegmental area (VTA) and increase DA levels within the nucleus accumbens and prefrontal cortex. We recorded from identified DA neuronal cell bodies within ventral midbrain slices prepared from a transgenic mouse line (TH-GFP) using long-term stable extracellular recordings in a variety of locations and carefully mapped the responses to applied ethanol (EtOH). We identified a subset of DA neurons in the medial VTA located within the rostral linear and interfascicular n…
Effect of depolarizing GABAA-mediated membrane responses on excitability of Cajal-Retzius cells in the immature rat neocortex
2011
In immature neurons activation of ionotropic GABA receptors induces depolarizing membrane responses due to a high intracellular Cl− concentration ([Cl−]i). However, it is difficult to draw conclusions about the functional consequences of subthreshold GABAergic depolarizations, since GABAergic membrane shunting and additional effects on voltage-dependent ion channels or action potential threshold must be considered. To systematically investigate factors that determine the GABAergic effect on neuronal excitability we performed whole cell patch-clamp recordings from Cajal-Retzius cells in immature rat neocortex, using [Cl−]i between 10 and 50 mM. The effect of focal GABA application was quant…
Sequential acquisition of cacophony calcium currents, sodium channels and voltage-dependent potassium currents affects spike shape and dendrite growt…
2014
During metamorphosis the CNS undergoes profound changes to accommodate the switch from larval to adult behaviors. In Drosophila and other holometabolous insects, adult neurons differentiate either from respecified larval neurons, newly born neurons, or are born embryonically but remain developmentally arrested until differentiation during pupal life. This study addresses the latter in the identified Drosophila flight motoneuron 5. In situ patch-clamp recordings, intracellular dye fills and immunocytochemistry address the interplay between dendritic shape, excitability and ionic current development. During pupal life, changes in excitability and spike shape correspond to a stereotyped, progr…
Muscle activity in upper and lower rectus abdominus during abdominal exercises.
1996
Abstract Objective: To compare the intensity of the upper versus lower rectus abdominis (RA) muscle activity provoked by each of two different abdominal exercises and to contrast the intensity of contraction elicited by two different abdominal exercises on each RA muscle portion. Design: Nonrandomized control trial. Setting: Kinesiology laboratory in a university medicine faculty. Participants: Convenience sample of 33 healthy volunteers. Subjects who had practiced endurance or strength training activities (1.5 hours 3 days a week for 3 years) and those who had not accomplished that criterion comprised a high and a low physical activity group, respectively. Each of these two groups was divi…
Novel modes of rhythmic burst firing at cognitively-relevant frequencies in thalamocortical neurons.
2008
It is now widely accepted that certain types of cognitive functions are intimately related to synchronized neuronal oscillations at both low (alpha/theta) (4-7/8-13 Hz) and high (beta/gamma) (18-35/30-70 Hz) frequencies. The thalamus is a key participant in many of these oscillations, yet the cellular mechanisms by which this participation occurs are poorly understood. Here we describe how, under appropriate conditions, thalamocortical (TC) neurons from different nuclei can exhibit a wide array of largely unrecognised intrinsic oscillatory activities at a range of cognitively-relevant frequencies. For example, both metabotropic glutamate receptor (mGluR) and muscarinic Ach receptor (mAchR) …
Three Patterns of Oscillatory Activity Differentially Synchronize Developing Neocortical Networks In Vivo
2009
Coordinated patterns of electrical activity are important for the early development of sensory systems. The spatiotemporal dynamics of these early activity patterns and the role of the peripheral sensory input for their generation are essentially unknown. We performed extracellular multielectrode recordings in the somatosensory cortex of postnatal day 0 to 7 rats in vivo and observed three distinct patterns of synchronized oscillatory activity. (1) Spontaneous and periphery-driven spindle bursts of 1-2 s in duration and approximately 10 Hz in frequency occurred approximately every 10 s. (2) Spontaneous and sensory-driven gamma oscillations of 150-300 ms duration and 30-40 Hz in frequency oc…