Calcium transients in subcompartments of the leech Retzius neuron as induced by single action potentials

2001 ◽  
Vol 48 (1) ◽  
pp. 1-18 ◽  
Author(s):  
Andreas Beck ◽  
Christian Lohr ◽  
Joachim W. Deitmer
Keyword(s):  
Action Potentials ◽  
Calcium Transients ◽  
Single Action ◽  
Retzius Neuron

Calcium transients in intact rat skeletal muscle fibers in agarose gel

1995 ◽  
Vol 269 (1) ◽  
pp. C28-C34 ◽  
Author(s):  
S. L. Carroll ◽  
M. G. Klein ◽  
M. F. Schneider
Keyword(s):  
Action Potentials ◽  
Time Course ◽  
Calcium Transients ◽  
Agarose Gel ◽  
Similar Time ◽  
Single Action ◽  
Fura 2 ◽  
Calcium Indicator ◽  
Flexor Digitorum Brevis ◽  
Time Courses

Intact single fibers enzymatically dissociated from rat flexor digitorum brevis muscle were suspended in 0.5% low-melting-temperature agarose gel to minimize fiber movement during action potentials or trains of action potentials. Resting Ca2+ concentration ([Ca2+]) and changes in [Ca2+] were monitored using the fluorescent calcium indicator fura 2. The time course and waveform of [Ca2+] transients during an action potential or trains of action potentials in fibers in agarose were calculated using kinetic parameters previously determined to correct for the calcium-fura 2 kinetic delay. Half times of the calculated calcium transients for single action potentials were 30-fold briefer than the original fura 2 signals. To confirm the time course and waveform of the calculated calcium transients, changes in [Ca2+] were monitored using the more rapidly equilibrating calcium indicator mag-fura 2. [Ca2+] transients for fibers containing fura 2 had very similar time courses and waveforms as mag-fura 2 signals from other fibers, indicating that the corrections for the calcium-fura 2 kinetic delay were accurate. The advantages of the agarose gel suspension are discussed.

Calcium Dynamics and Compartmentalization in Leech Neurons

2005 ◽  
Vol 94 (6) ◽  
pp. 4430-4440 ◽  
Author(s):  
Sofija Andjelic ◽  
Vincent Torre
Keyword(s):  
Information Processing ◽  
Action Potential ◽  
Action Potentials ◽  
Time Course ◽  
Ccd Camera ◽  
Calcium Dynamics ◽  
Single Action ◽  
Single Action Potential ◽  
Calcium Indicator ◽  
Mechanosensory Neurons

Calcium dynamics in leech neurons were studied using a fast CCD camera. Fluorescence changes (Δ F/ F) of the membrane impermeable calcium indicator Oregon Green were measured. The dye was pressure injected into the soma of neurons under investigation. Δ F/ F caused by a single action potential (AP) in mechanosensory neurons had approximately the same amplitude and time course in the soma and in distal processes. By contrast, in other neurons such as the Anterior Pagoda neuron, the Annulus Erector motoneuron, the L motoneuron, and other motoneurons, APs evoked by passing depolarizing current in the soma produced much larger fluorescence changes in distal processes than in the soma. When APs were evoked by stimulating one distal axon through the root, Δ F/ F was large in all distal processes but very small in the soma. Our results show a clear compartmentalization of calcium dynamics in most leech neurons in which the soma does not give propagating action potentials. In such cells, the soma, while not excitable, can affect information processing by modulating the sites of origin and conduction of AP propagation in distal excitable processes.

Structure and Function of the Lateral Giant Neurone of the Primitive Crustacean Anaspides Tasmaniae

1979 ◽  
Vol 78 (1) ◽  
pp. 121-136
Author(s):  
GERALD E. SILVEY ◽  
IAN S. WILSON
Keyword(s):  
Action Potentials ◽  
Tactile Stimulation ◽  
Large Diameter ◽  
Whole Body ◽  
Giant Fibre ◽  
Single Action ◽  
Giant Neurone ◽  
And Function ◽  
Thoracic And Abdominal ◽  
Stimulation Of

The syncarid crustacean Anaspides tasmaniae rapidly flexes its free thoracic and abdominal segments in response to tactile stimulation of its body. This response decrements but recovers in slightly more than one hour. The fast flexion is evoked by single action potentials in the lateral of two large diameter fibres (40 μm) which lie on either side of the cord. The lateral giant fibre is made up of fused axons of 11 neurones, one in each of the last 5 thoracic and 6 abdominal ganglia. The soma of each neurone lies contralateral to the axon. Its neurite crosses that of its counterpart in the commissure and gives out dendrites into the neuropile of each hemiganglion. The lateral giant neurone receives input from the whole body but fires in response only to input from the fourth thoracic segment posteriorly. Both fibres respond with tactile stimulation of only one side. Since neither current nor action potentials spread from one fibre to the other, afferents must synapse with both giant neurones. The close morphological and physiological similarities of the lateral giant neurone in Anaspides to that in the crayfish (Eucarida) suggest that the lateral giant system arose in the ancestor common to syncarids and eucarids, prior to the Carboniferous.

Electrophysiological properties of neurons within the nucleus ambiguus of adult guinea pigs

1991 ◽  
Vol 66 (3) ◽  
pp. 744-761 ◽  
Author(s):  
S. M. Johnson ◽  
P. A. Getting
Keyword(s):  
Action Potential ◽  
Action Potentials ◽  
Outward Current ◽  
Nucleus Ambiguus ◽  
Transient Outward Current ◽  
Maximum Magnitude ◽  
Action Potential Firing ◽  
Onset Of Action ◽  
Electrophysiological Properties ◽  
Single Action

1. The purpose of this study was to determine the electrophysiological properties of neurons within the region of the nucleus ambiguus (NA), an area that contains the ventral respiratory group. By the use of an in vitro brain stem slice preparation, intracellular recordings from neurons in this region (to be referred to as NA neurons, n = 235) revealed the following properties: postinhibitory rebound (PIR), delayed excitation (DE), adaptation, and posttetanic hyperpolarization (PTH). NA neurons were separated into three groups on the basis of their expression of PIR and DE: PIR cells (58%), DE cells (31%), and Non cells (10%). Non cells expressed neither PIR nor DE and no cells expressed both PIR and DE. 2. PIR was a transient depolarization that produced a single action potential or a burst of action potentials when the cell was released from hyperpolarization. In the presence of tetrodotoxin (TTX), the maximum magnitude of PIR was 7-12 mV. Under voltage-clamp conditions, hyperpolarizing voltage steps elicited a small inward current during the hyperpolarization and a small inward tail current on release from hyperpolarization. These currents, which mediate PIR, were most likely due to Q-current because they were blocked with extracellular cesium and were insensitive to barium. 3. DE was a delay in the onset of action potential firing when cells were hyperpolarized before application of depolarizing current. When cells were hyperpolarized to -90 mV for greater than or equal to 300 ms, maximum delays ranged from 150 to 450 ms. The transient outward current underlying DE was presumed to be A-current because of the current's activation and inactivation characteristics and its elimination by 4-aminopyridine (4-AP). 4. Adaptation was examined by applying depolarizing current for 2.0 s and measuring the frequency of evoked action potentials. Although there was a large degree of variability in the degree of adaptation, PIR cells tended to express less adaptation than DE and Non cells. Nearly three-fourths of all NA neurons adapted rapidly (i.e., 50% adaptation in less than 200 ms), but PIR cells tended to adapt faster than DE and Non cells. PTH after a train of action potentials was relatively rare and occurred more often in DE cells (43%) and Non cells (33%) than in PIR cells (13%). PTH had a magnitude of up to 18 mV and time constants that reflected the presence of one (1.7 +/- 1.4 s, mean +/- SD) or two components (0.28 +/- 0.13 and 4.1 +/- 2.2 s).(ABSTRACT TRUNCATED AT 400 WORDS)

Excitable Membrane Properties of Neurons

2020 ◽  
Author(s):  
Leonard K. Kaczmarek
Keyword(s):  
Action Potential ◽  
Action Potentials ◽  
Cell Biology ◽  
Neuronal Firing ◽  
Membrane Properties ◽  
Potassium Ions ◽  
Single Action ◽  
Sodium Calcium ◽  
Different Types ◽  
Order Of Magnitude

The intrinsic electrical properties of neurons are extremely varied. For example, the width of action potentials in different neurons varies by more than an order of magnitude. In response to prolonged stimulation, some neurons generate repeated action potential hundreds of times a second, while others fire only a single action potential or adapt very rapidly. These differences result from the expression of different types of ion channels in the plasma membrane. The dominant channels that shape neuronal firing patterns are those that are selective for sodium, calcium, and potassium ions. This chapter provides a brief overview of the biophysical properties of each of these classes of channel, their role in shaping the electrical personality of a neuron, and how interactions of these channels with cytoplasmic factors shape the overall cell biology of a neuron.

Sensory feedback and central afferent interaction in the muscle receptor organ of the crab, Carcinus maenas

1996 ◽  
Vol 76 (2) ◽  
pp. 788-798 ◽  
Author(s):  
M. Wildman ◽  
A. Cannone
Keyword(s):  
Action Potentials ◽  
Sensory Feedback ◽  
Carcinus Maenas ◽  
Small Diameter ◽  
Sensory Response ◽  
Fiber Direction ◽  
Single Action ◽  
Muscle Receptor ◽  
Leg Muscles ◽  
Receptor Organ

1. An interaction exists between two proprioceptive afferent neurons innervating the thoracic-coxal muscle receptor organ (TCMRO) of the crab, Carcinus maenas. Intracellular recordings were made from the extraganglionic regions of the afferents in order to characterize this interaction and its effects on sensory feedback. 2. A current-induced depolarization of the nonspiking T fiber of the TCMRO results in a depolarization of the P fiber, a small-diameter (7 microns) neuron innervating the same receptor. This interaction is graded in amplitude, and may result in a single action potential being superimposed on the graded response of the P fiber. A hyperpolarization of the T fiber has a smaller effect on the P fiber than a depolarization of similar amplitude. The interaction is rectified in a T- to P-fiber direction, and has a minimum central delay of approximately 3.6 ms. 3. The site of the interaction between the afferents is situated centrally, within the thoracic ganglion. Action potentials evoked in the P fiber by a T-fiber depolarization propagate actively and antidromically to the periphery. 4. Central modulation of the interaction occurs, because the amplitude of a T-fiber-induced depolarization is reduced in the P fiber during centrally generated spontaneous bursts of activity in the motoneurons of basal leg muscles. 5. Because of the interaction between T and P fibers, action potentials recorded from the peripheral portion of the P fiber during receptor stretch may be either orthodromic, resulting directly from the effects of the stretch on the sensory endings of the P fiber, or antidromic, resulting from the central input from the T fiber. 6. The T- to P-fiber interaction may serve to extend the dynamic sensitivity range of the P fiber, in particular by amplifying its sensory response at short receptor lengths and low velocities of stretch.

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