scholarly journals Voltage-activated currents in identified giant interneurons isolated from adult crickets gryllus bimaculatus

1998 ◽  
Vol 201 (17) ◽  
pp. 2529-2541 ◽  
Author(s):  
P Kloppenburg ◽  
M Hörner
Keyword(s):  
Action Potentials ◽  
Gryllus Bimaculatus ◽  
Selective Labeling ◽  
Electrophysiological Properties ◽  
Giant Interneurons ◽  
Whole Cell Patch Clamp ◽  
Unequivocal Identification ◽  
Ionic Mechanisms ◽  
K Currents

The electrophysiological properties of cultured giant interneurons isolated from the terminal ganglion of adult crickets (Gryllus bimaculatus) were investigated using whole-cell patch-clamp techniques. To allow for unequivocal identification of these interneurons in cell culture, a protocol for fast and selective labeling of their cell bodies was established. Prior to cell dissociation, the giant interneurons were backfilled through their axons in situ with a fluorescent dye (dextran tetramethylrhodamine). In primary cell cultures, the cell bodies of giant interneurons were identified among a population of co-cultured neurons by their red fluorescence. Action potentials were recorded from the cell bodies of the cultured interneurons suggesting that several types of voltage-activated ion channels exist in these cells. Using voltage-clamp recording techniques, four voltage-activated currents were isolated and characterized. The giant interneurons express at least two distinct K+ currents: a transient current that is blocked by 4-aminopyridine (4x10(-3 )mol l-1) and a sustained current that is partially blocked by tetraethylammonium (3x10(-2 )mol l-1) and quinidine (2x10(-4 )mol l-1). In addition, a transient Na+ current sensitive to 10(-7 )mol l-1 tetrodotoxin and a Ca2+ current blocked by 5x10(-4 )mol l-1 CdCl2 have been characterized. This study represents the first step in an attempt to analyze the cellular and ionic mechanisms underlying plasticity in the well-characterized and behaviorally important giant interneuron pathway in insects.

scholarly journals Cardiac Transmembrane Ion Channels and Action Potentials: Cellular Physiology and Arrhythmogenic Behavior

2020 ◽  
Author(s):  
András Varró ◽  
Jakub Tomek ◽  
Norbert Nagy ◽  
Laszlo Virag ◽  
Elisa Passini ◽  
...  
Keyword(s):  
Ion Channel ◽  
Action Potentials ◽  
Cardiac Electrophysiology ◽  
Current Knowledge ◽  
Animal Experiments ◽  
Cardiac Cells ◽  
Cellular Mechanisms ◽  
Electrophysiological Properties ◽  
Channel Expression ◽  
Ionic Mechanisms

Cardiac arrhythmias are among the leading causes of mortality. They often arise from alterations in the electrophysiological properties of cardiac cells, and their underlying ionic mechanisms. It is therefore critical to further unravel the patho-physiology of the ionic basis of human cardiac electrophysiology in health and disease. In the first part of this review, current knowledge on the differences in ion channel expression and properties of the ionic processes that determine the morphology and properties of cardiac action potentials and calcium dynamics from cardiomyocytes in different regions of the heart are described. Then the cellular mechanisms promoting arrhythmias in congenital or acquired conditions of ion channel function (electrical remodelling) are discussed. The focus is human relevant findings obtained with clinical, experimental and computational studies, given that interspecies differences make the extrapolation from animal experiments to the human clinical settings difficult. Deepening the understanding of the diverse patholophysiology of human cellular electrophysiology will help developing novel and effective antiarrhythmic strategies for specific subpopulations and disease conditions.

scholarly journals Intrinsic excitability differs between murine hypoglossal and spinal motoneurons

2016 ◽  
Vol 115 (5) ◽  
pp. 2672-2680 ◽  
Author(s):  
M. A. Tadros ◽  
A. J. Fuglevand ◽  
A. M. Brichta ◽  
R. J. Callister
Keyword(s):  
Action Potentials ◽  
Membrane Properties ◽  
Intrinsic Excitability ◽  
Spinal Motoneurons ◽  
Patch Clamp Recording ◽  
Electrophysiological Properties ◽  
Hypoglossal Motoneurons ◽  
Whole Cell Patch Clamp ◽  
Two Populations ◽  
Passive Membrane Properties

Motoneurons differ in the behaviors they control and their vulnerability to disease and aging. For example, brain stem motoneurons such as hypoglossal motoneurons (HMs) are involved in licking, suckling, swallowing, respiration, and vocalization. In contrast, spinal motoneurons (SMs) innervating the limbs are involved in postural and locomotor tasks requiring higher loads and lower movement velocities. Surprisingly, the properties of these two motoneuron pools have not been directly compared, even though studies on HMs predominate in the literature compared with SMs, especially for adult animals. Here we used whole cell patch-clamp recording to compare the electrophysiological properties of HMs and SMs in age-matched neonatal mice (P7–P10). Passive membrane properties were remarkably similar in HMs and SMs, and afterhyperpolarization properties did not differ markedly between the two populations. HMs had narrower action potentials (APs) and a faster upstroke on their APs compared with SMs. Furthermore, HMs discharged APs at higher frequencies in response to both step and ramp current injection than SMs. Therefore, while HMs and SMs have similar passive properties, they differ in their response to similar levels of depolarizing current. This suggests that each population possesses differing suites of ion channels that allow them to discharge at rates matched to the different mechanical properties of the muscle fibers that drive their distinct motor functions.

K+ currents responsible for repolarization in mouse ventricle and their modulation by FK-506 and rapamycin

2000 ◽  
Vol 278 (3) ◽  
pp. H886-H897 ◽  
Author(s):  
W. H. DuBell ◽  
W. J. Lederer ◽  
T. B. Rogers
Keyword(s):  
Action Potential ◽  
Action Potentials ◽  
Regulatory Proteins ◽  
Channel Blockers ◽  
Patch Clamp Technique ◽  
Fk 506 ◽  
Transient Component ◽  
Whole Cell Patch Clamp ◽  
Recovery From Inactivation ◽  
K Currents

Modulation of mouse ventricular action potentials and K+ currents was examined using the whole cell patch-clamp technique. The composite mouse ventricular K+ current (consisted of an outward transient followed by a slowly decaying sustained component. Use of the K+ channel blockers tetraethylammonium and 4-aminopyridine and a transgenic mouse model revealed three pharmacologically and kinetically distinct currents: I to, which contributed to the transient component; I K, which contributed to the sustained component; and a slowly activating current ( I slow), which contributed to both components. The immunosuppressant FK-506 increased action potential duration at 90% repolarization by 66.7% by decreasing the sustained component (−48% at +60 mV) and prolonging recovery from inactivation (by 26% at 200 ms) of the transient component. These effects were isolated to I K and I to, respectively. Rapamycin had strikingly similar effects on these currents. Both FK-506 and rapamycin are known to target the immunophilin FKBP12. Thus we conclude that FKBP12 modulates specific mouse K+ channels, and thus the mouse ventricular action potential, by interacting directly with K+ channel proteins or with other associated regulatory proteins.

Electrophysiological properties of identified classes of lamprey spinal neurons

1993 ◽  
Vol 70 (6) ◽  
pp. 2313-2325 ◽  
Author(s):  
J. T. Buchanan
Keyword(s):  
Action Potential ◽  
Current Pulse ◽  
Action Potentials ◽  
The Other ◽  
Resting Potential ◽  
Spinal Neurons ◽  
Electrophysiological Properties ◽  
Giant Interneurons ◽  
Significant Difference ◽  
Sensory Processes

1. As part of a continuing analysis of the mechanisms of the central pattern generator underlying fictive swimming in lamprey, a systematic survey of electrophysiological properties of lamprey neurons was made in the in vitro spinal cord preparation with the use of intracellular current-clamp recordings. A total of 70 neurons was included in the study, representing 6 classes of spinal neurons. The classes were myotomal motoneurons, three classes of interneurons involved in fictive swimming [lateral interneurons, nerve cells with contralateral and caudal projecting axons (CC interneurons), and excitatory interneurons], and two classes of interneurons involved in sensory processes (edge cells and giant interneurons). The recordings were done in quiescent preparations. 2. There was little or no significant difference among the cell classes with regard to resting potential, threshold potential, action-potential amplitude, or action-potential duration. 3. The voltage versus current relationships for the cells were fairly linear near resting potential, although most cells showed a slight tendency to rectify with depolarization above resting potential. This tendency was strongest among edge cells and lateral interneurons and weakest among motoneurons and CC interneurons. The input resistances, membrane time constants, and rheo-bases for the cell classes showed significant differences among some classes. For example, CC interneurons and excitatory interneurons had significantly higher input resistances than the other cell classes. 4. The late afterhyperpolarization following the action potential tended to be larger in amplitude with an earlier peak and a longer duration in edge cells and giant interneurons than in the other cell classes. 5. All cells responded to depolarizing current injections by firing action potentials, and almost all cells fired action potentials throughout the 400-ms current pulse. The cells exhibited adaptation resulting in increasing interspike intervals during the current pulse. The adaptation, however, was insufficient to terminate firing before the end of the current pulse. The relationship between frequency of firing and input current was generally monotonic with a tendency to saturate at higher current levels. 6. The general conclusion from this study is that the spinal neurons that partake in fictive swimming (motoneurons, lateral interneurons, CC interneurons, and excitatory interneurons) are similar in their resting and action-potential mechanisms. Their most prominent differences are in size-related properties. The sensory-related interneurons, especially the edge cells and to some extent the giant interneurons, exhibited more pronounced differences in their resting and action-potential properties when compared with the other cell classes.

scholarly journals The Electrophysiology of Cnidocytes

1987 ◽  
Vol 133 (1) ◽  
pp. 215-230 ◽  
Author(s):  
PETER A. V. ANDERSON ◽  
M. CRAIG MCKAY
Keyword(s):  
Action Potentials ◽  
Ionic Currents ◽  
Na Current ◽  
Selective Blockade ◽  
Current Voltage ◽  
Inward Currents ◽  
K Current ◽  
A Current ◽  
K Currents

Electrical properties of cnidocytes isolated from the hydroid Cladonema and the scyphomedusa Chrysaora were examined using current- and voltage-clamp recording techniques. The stenoteles of Cladonema produced action potentials when depolarized above 0 m V. The inward current that produced the action potential was a Na+ current. These cells also possessed an A-current and a K-current. Atrichous isorhizas from Chrysaora did not spike and did not have any inward currents. All cells examined had K-currents, some had A-currents also. Very few cnidocytes discharged during the course of the recordings, irrespective of the degree to which they were depolarized or hyperpolarized, or the presence or selective blockade of any ionic currents. When discharge did occur it could never be correlated with any obvious electrophysiological event. Recordings from cnidocytes in situ in tentacles of the siphonophore Physalia indicate that these cells do not spike. Their current/voltage relationships were linear. They too did not discharge in response to changes in membrane potential, suggesting that the failure of isolated cnidocytes to discharge cannot be attributed to the isolation procedure.

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