Membrane Properties Related to the Firing Behavior of Zebrafish Motoneurons

2003 ◽  
Vol 89 (2) ◽  
pp. 657-664 ◽  
Author(s):  
Robert R. Buss ◽  
Charles W. Bourque ◽  
Pierre Drapeau
Keyword(s):  
Action Potential ◽  
Action Potentials ◽  
Membrane Conductance ◽  
Membrane Properties ◽  
High Threshold ◽  
Calcium Dependent ◽  
Larval Zebrafish ◽  
Plateau Potential ◽  
Potassium Conductances ◽  
Action Potential Burst

The physiological and pharmacological properties of the motoneuron membrane and action potential were investigated in larval zebrafish using whole cell patch current-clamp recording techniques. Action potentials were eliminated in tetrodotoxin, repolarized by tetraethylammonium (TEA) and 3,4-diaminopyridine (3,4-AP)-sensitive potassium conductances, and had a cobalt-sensitive, high-threshold calcium component. Depolarizing current injection evoked a brief (approximately 10–30 ms) burst of action potentials that was terminated by strong, outwardly rectifying voltage-activated potassium and calcium-dependent conductances. In the presence of intracellular cesium ions, a prolonged plateau potential often followed brief depolarizations. During larval development (hatching to free-swimming), the resting membrane conductance increased in a population of motoneurons, which tended to reduce the apparent outward rectification of the membrane. The conductances contributing to action potential burst termination are hypothesized to play a role in patterning the synaptically driven motoneuron output in these rapidly swimming fish.

scholarly journals Action Potentials in Rhodnius Oocytes: Repolarization is Sensitive to Potassium Channel Blockers

1986 ◽  
Vol 126 (1) ◽  
pp. 119-132
Author(s):  
M. J. O'DONNELL
Keyword(s):  
Potassium Channel ◽  
Action Potentials ◽  
Potassium Conductance ◽  
Channel Blockers ◽  
Calcium Dependent ◽  
Outward Rectification ◽  
Current Voltage ◽  
Potassium Channel Blockers ◽  
Potassium Conductances ◽  
Voltage Dependent

Depolarization of Rhodnius oocytes evokes action potentials (APs) whose rising phase is calcium-dependent. The ionic basis for the repolarizing (i.e. falling) phase of the AP was examined. Addition of potassium channel blockers (tetraethylammonium, tetrabutylammonium, 4-aminopyridine, atropine) to the bathing saline increased the duration and overshoot of APs. Intracellular injection of tetraethyl ammonium had similar effects. These results suggest that a voltage-dependent potassium conductance normally contributes to repolarization. Repolarization does not require a chloride influx, because substitution of impermeant anions for chloride did not increase AP duration. AP duration and overshoot actually decreased progressively when chloride levels were reduced. Current/voltage curves show inward and outward rectification, properties often associated with potassium conductances. Outward rectification was largely blocked by external tetraethylammonium. Possible functions of the rectifying properties of the oocyte membrane are discussed.

scholarly journals Calcium-Dependent Action Potentials in the Second-Order Neurones of Cockroach Ocelli

1987 ◽  
Vol 130 (1) ◽  
pp. 259-274
Author(s):  
MAKOTO MIZUNAMI ◽  
SHIGEKI YAMASHITA ◽  
HIDEKI TATEDA
Keyword(s):  
Action Potential ◽  
Action Potentials ◽  
Periplaneta Americana ◽  
Fold Increase ◽  
Second Order ◽  
Calcium Currents ◽  
Light Responses ◽  
Calcium Dependent ◽  
Major Carrier ◽  
Visual Neurones

The ionic basis of the action potential in the large second-order neurones (L-neurones) of the ocellus of the cockroach, Periplaneta americana, was studied. L-neurones generated action potentials, usually once, at the off-set of hyperpolarizing light responses, or at the termination of hyperpolarizing current stimuli. The action potential was blocked by replacing saline Ca2+ with Mg2+ but maintained when Ba2+ was substituted. A block was produced by 2 mmoll l−1 Cd2+ or 20 mmol l−l Co2+. The peak amplitude of the action potential increased by 26 mV for a 10-fold increase in external Ca2+ concentration, at concentrations below 1.8 mmol l−1. The action potential was not affected by sodium-free saline or by 3×10−6mol l−1 tetrodotoxin (TTX). These observations suggest that calcium ions are the major carrier for the inward current of the action potential. This finding supports the suggestion that the off-set responses of hyperpolarizing visual neurones of both vertebrates and invertebrates have a common ionic mechanism, including voltage-sensitive calcium currents.

Resting and Active Properties of Pyramidal Neurons in Subiculum and CA1 of Rat Hippocampus

2000 ◽  
Vol 84 (5) ◽  
pp. 2398-2408 ◽  
Author(s):  
Nathan P. Staff ◽  
Hae-Yoon Jung ◽  
Tara Thiagarajan ◽  
Michael Yao ◽  
Nelson Spruston
Keyword(s):  
Action Potential ◽  
Action Potentials ◽  
Pyramidal Neurons ◽  
Current Injection ◽  
Synaptic Integration ◽  
Membrane Properties ◽  
Neuronal Membrane ◽  
Similar Action ◽  
Ca1 Neurons ◽  
Ca1 Pyramidal Neurons

Action potentials are the end product of synaptic integration, a process influenced by resting and active neuronal membrane properties. Diversity in these properties contributes to specialized mechanisms of synaptic integration and action potential firing, which are likely to be of functional significance within neural circuits. In the hippocampus, the majority of subicular pyramidal neurons fire high-frequency bursts of action potentials, whereas CA1 pyramidal neurons exhibit regular spiking behavior when subjected to direct somatic current injection. Using patch-clamp recordings from morphologically identified neurons in hippocampal slices, we analyzed and compared the resting and active membrane properties of pyramidal neurons in the subiculum and CA1 regions of the hippocampus. In response to direct somatic current injection, three subicular firing types were identified (regular spiking, weak bursting, and strong bursting), while all CA1 neurons were regular spiking. Within subiculum strong bursting neurons were found preferentially further away from the CA1 subregion. Input resistance ( R N), membrane time constant (τm), and depolarizing “sag” in response to hyperpolarizing current pulses were similar in all subicular neurons, while R N and τm were significantly larger in CA1 neurons. The first spike of all subicular neurons exhibited similar action potential properties; CA1 action potentials exhibited faster rising rates, greater amplitudes, and wider half-widths than subicular action potentials. Therefore both the resting and active properties of CA1 pyramidal neurons are distinct from those of subicular neurons, which form a related class of neurons, differing in their propensity to burst. We also found that both regular spiking subicular and CA1 neurons could be transformed into a burst firing mode by application of a low concentration of 4-aminopyridine, suggesting that in both hippocampal subfields, firing properties are regulated by a slowly inactivating, D-type potassium current. The ability of all subicular pyramidal neurons to burst strengthens the notion that they form a single neuronal class, sharing a burst generating mechanism that is stronger in some cells than others.

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.

Dendrotoxin blocks accommodation in frog myelinated axons

1989 ◽  
Vol 62 (1) ◽  
pp. 174-184 ◽  
Author(s):  
M. O. Poulter ◽  
T. Hashiguchi ◽  
A. L. Padjen
Keyword(s):  
Action Potential ◽  
Computer Model ◽  
Action Potentials ◽  
Potassium Conductance ◽  
Constant Stimulus ◽  
Motor Axons ◽  
Myelinated Axons ◽  
Frequency Adaptation ◽  
Potassium Conductances ◽  
Slow Potassium

1. Intracellular microelectrode recordings from large sensory and motor myelinated axons in spinal roots of Rana pipiens were used to study the effects of dendrotoxin (DTX), a specific blocker of a fast activating potassium current (GKf1). 2. Dendrotoxin reduced the ability of myelinated sensory and motor axons to accommodate to a constant stimulus. A depolarizing current step, which normally evoked only one action potential, after dendrotoxin treatment (200-500 nM) produced a train of action potentials. These spike trains lasted 29 +/- 2.8 (SE) ms on average in sensory fibers (n = 18) and 40.2 +/- 4.5 ms in motor fibers (n = 9). 3. After dendrotoxin treatment, in addition to a reduction in the ability to accommodate to a constant stimulus, a slowing in the rate of action potential generation was evident (spike frequency adaptation). 4. Dendrotoxin had no effect on the rising phase of conducted action potentials evoked by peripheral stimulation. Together with a lack of effect on the absolute refractory period, these results indicate that dendrotoxin does not affect sodium channel activity. 5. The steady-state voltage/current relationship was unchanged in response to hyperpolarizing current pulses; however, there was a significant increase in cord resistance in response to depolarizing current steps, demonstrating that DTX decreases outward rectification. 6. A computer model based on Hodgkin and Huxley equations was developed, which included the three voltage-dependent potassium conductances described by Dubois. The model reproduced major experimental results: removal of the conductance, termed GKf1, reduced the accommodation in the early phase of a continuous stimulus, indicating that this current could be responsible for the early accommodation. The hypothesis that the slow potassium conductance GKs regulates late accommodation and action potential frequency adaptation is also supported by the computer model. 7. In summary, these results suggest that in amphibian myelinated sensory and motor axons, the activity of potassium conductances can account for accommodation and adaptation without involvement of sodium conductance activity.

Calcium currents of cardiovascular neurons isolated from adult guinea pigs

1987 ◽  
Vol 252 (4) ◽  
pp. H867-H871
Author(s):  
D. L. Kunze
Keyword(s):  
Guinea Pigs ◽  
Action Potentials ◽  
Calcium Current ◽  
Threshold Current ◽  
Bipolar Cells ◽  
Calcium Currents ◽  
High Threshold ◽  
Calcium Dependent ◽  
Low Threshold ◽  
Patch Technique

A preparation of cells isolated from the medial and dorsal nuclei of the solitary tract of the medulla of adult guinea pigs was developed to examine the electrical properties of neurons isolated from an area of the central nervous system which is involved in the control of arterial pressure and heart rate. Bipolar cells of approximately 10 microns diameter were obtained on enzymatic dispersion. The cells were studied with the use of the patch technique for whole cell recording. Action potentials were elicited by depolarizing pulses in the presence of 10(-5) M tetrodotoxin which blocked a sodium-dependent current. These action potentials were calcium dependent and were eliminated by adding 1 mM Cd to the bath. In all cells studied, two voltage-dependent components to the calcium current were identified. In 10 mM Ca a high-threshold component activated at approximately -20 mV from holding potentials of -30 mV. A second lower threshold component was activated at -40 mV from more negative holding potentials of -80 mV. The low-threshold component was rapidly inactivating, whereas the high-threshold current slowly inactivated. The peak amplitudes of the two components were similar. Both components were blocked by 1 mM Cd. A role for the low-threshold calcium current in generating repetitive activity is postulated.

scholarly journals A Mathematical Model for the Cardiac Action Potential Based on Slow Inactivation of Sodium Conductance

1968 ◽  
Vol 21 (1) ◽  
pp. 37 ◽  
Author(s):  
L Munk ◽  
E PGeorge
Keyword(s):  
Mathematical Model ◽  
Action Potential ◽  
Action Potentials ◽  
Sodium Current ◽  
Potassium Conductance ◽  
Slow Inactivation ◽  
Squid Axon ◽  
Purkinje Fibres ◽  
Cardiac Action ◽  
Potassium Conductances

A mathematical model for the action potential in Purkinje fibres is developed. It is based on voltage-clamp results which show that inactivation of sodium current in these muscles is much slower than in squid axon and that the latent rise in potassium conductance is not present. Both the sodium and the potassium conductances are represented as a sum of slow and fast components. This is incorporated in the suitably adjusted Hodgkin-Huxley model for the squid axon. It is shown that such a model can account satisfactorily for the shape of the action potentials in Purkinje fibres.

Biophysical Properties and Responses to Neurotransmitters of Petrosal and Geniculate Ganglion Neurons Innervating the Tongue

2000 ◽  
Vol 84 (3) ◽  
pp. 1404-1413 ◽  
Author(s):  
Tomoshige Koga ◽  
Robert M. Bradley
Keyword(s):  
Action Potential ◽  
Action Potentials ◽  
Membrane Properties ◽  
Patch Clamp Recording ◽  
Potential Decay ◽  
Ganglion Neurons ◽  
Fast Rise ◽  
Posterior Tongue ◽  
Passive Membrane Properties

The properties of afferent sensory neurons supplying taste receptors on the tongue were examined in vitro. Neurons in the geniculate (GG) and petrosal ganglia (PG) supplying the tongue were fluorescently labeled, acutely dissociated, and then analyzed using patch-clamp recording. Measurement of the dissociated neurons revealed that PG neurons were significantly larger than GG neurons. The active and passive membrane properties of these ganglion neurons were examined and compared with each other. There were significant differences between the properties of neurons in the PG and GG ganglia. The mean membrane time constant, spike threshold, action potential half-width, and action potential decay time of GG neurons was significantly less than those of PG neurons. Neurons in the PG had action potentials that had a fast rise and fall time (sharp action potentials) as well as action potentials with a deflection or hump on the falling phase (humped action potentials), whereas action potentials of GG neurons were all sharp. There were also significant differences in the response of PG and GG neurons to the application of acetylcholine (ACh), serotonin (5HT), substance P (SP), and GABA. Whereas PG neurons responded to ACh, 5HT, SP, and GABA, GG neurons only responded to SP and GABA. In addition, the properties of GG neurons were more homogeneous than those of the PG because all the GG neurons had sharp spikes and when responses to neurotransmitters occurred, either all or most of the neurons responded. These differences between neurons of the GG and PG may relate to the type of receptor innervated. PG ganglion neurons innervate a number of receptor types on the posterior tongue and have more heterogeneous properties, while GG neurons predominantly innervate taste buds and have more homogeneous properties.

Membrane properties and synaptic responses of the guinea pig nucleus accumbens neurons in vitro

1989 ◽  
Vol 61 (4) ◽  
pp. 769-779 ◽  
Author(s):  
N. Uchimura ◽  
H. Higashi ◽  
S. Nishi
Keyword(s):  
Membrane Potential ◽  
Nucleus Accumbens ◽  
Guinea Pig ◽  
Action Potential ◽  
Action Potentials ◽  
Reversal Potential ◽  
Membrane Properties ◽  
Current Pulses ◽  
Synaptic Responses

1. The membrane properties and synaptic responses of guinea pig nucleus accumbens neurons in vitro were studied with intracellular recording methods. 2. The population of neurons could be divided into groups of low (20-60 M omega, average 46.5 M omega) and high (60-180 M omega, average 96.5 M omega) input resistance. The resting membrane potential in both groups was approximately -70 mV. 3. Other membrane properties were quite similar in both groups. Inward rectification occurred at potentials more negative than -80 mV; this was blocked by Cs+ (2 mM). Membrane potential oscillations were observed at potentials between -65 and -55 mV; these were blocked by tetrodotoxin (TTX, 0.5 microM). Outward rectification occurred at potentials less negative than -45 mV; this was depressed by tetraethylammonium (TEA, 10 mM). 4. Action potentials elicited by small depolarizing current pulses (2-5 ms, 0.3-0.5 nA) were approximately 95 mV in amplitude and 1.0 ms in duration. The afterhyperpolarization following each action potential was less than 30 ms in duration, and no accommodation of action-potential discharge was seen at frequencies up to 40 Hz. The action potentials were reversibly blocked by TTX (0.3 microM). In addition, TTX-insensitive, Ca2+-dependent spikes were evoked by passing larger and more prolonged current pulses (greater than 40 ms, greater than 0.5 nA) across the membrane. 5. Focal electrical stimulation of the slice surface with low intensity (1 ms, less than 10 V) elicited excitatory postsynaptic potentials (EPSPs) in neurons of both high- and low-resistance groups. The reversal potential (+10.2 mV) for the EPSPs was close to the reversal potential (+7.7 mV) of the responses to glutamate applied in the superfusing solution. The N-methyl-D-aspartic acid (NMDA) receptor antagonists, D-alpha-aminoadipic acid (1 mM) and DL-2-amino-5-phosphonovaleric acid (DL-APV, 250 microM), reversibly depressed the EPSP; the glutamate uptake inhibitor, L-aspartic acid-beta-hydroxamate (50 microM), or removal of Mg2+ from the superfusate, augmented the EPSP. 6. When the intensity of the focal stimulus was increased (1 ms, greater than or equal to 10 V), a second larger depolarizing response (duration, 800 ms to 2 s) could be evoked in addition to the smoothly graded EPSP. This was seen only in cells of the high-resistance group (90-130 M omega).(ABSTRACT TRUNCATED AT 400 WORDS)

Electrical properties of oxytocin neurons in organotypic cultures from postnatal rat hypothalamus

1996 ◽  
Vol 76 (4) ◽  
pp. 2772-2785 ◽  
Author(s):  
P. Jourdain ◽  
D. A. Poulain ◽  
D. T. Theodosis ◽  
J. M. Israel
Keyword(s):  
Electrical Properties ◽  
Action Potential ◽  
Glutamate Receptors ◽  
Action Potentials ◽  
Firing Pattern ◽  
Membrane Conductance ◽  
Input Resistance ◽  
Resting Potential ◽  
Organotypic Cultures ◽  
Current Pulses

1. Intracellular recordings were performed on immunocytochemically identified oxytocin (OT) neurons (n = 101) maintained for 2-7 wk in hypothalamic organotypic cultures derived from 4-to 6-day-old rat neonates. The neurons displayed a resting potential of -58.9 +/- 6.8 mV (mean +/- SD, n = 74), an input resistance of 114 +/- 26.8 M omega (n = 66), and a time constant of 9.6 +/- 1.4 ms (n = 57). Voltage-current (V-I) relations, linear at resting potential, showed a pronounced outward rectification when depolarized from hyperpolarized membrane potentials. At these hyperpolarized potentials, depolarizing current pulses induced a delayed action potential. 2. Action potentials had an amplitude of 73.4 +/- 9.7 mV and a duration of 1.9 +/- 0.2 ms. Each action potential was followed by an afterhyperpolarization of 7.9 +/- 2.0 mV in amplitude lasting 61.7 +/- 11.3 ms. The depolarizing phase of action potentials was both Na+ and Ca2+ dependent, whereas repolarization was due to a K+ conductance increase. 3. When Ba2+ was substituted for Ca2+ in the medium, OT neurons displayed prolonged sustained depolarizations. In the presence of tetrodotoxin (TTX), these depolarizations were triggered by depolarizing current pulses and arrested by hyperpolarizing current pulses or by local application of Ca2+, Co2+, Cd2+, No sustained depolarization was obtained when nifedipine was added to the medium. These data suggest that OT cells in organotypic culture possess L-type Ca2+ channels. 4. All OT neurons generated spontaneous action potentials at resting potential. Of 59 neurons, 29 showed a slow, irregular firing pattern (< or = 2.5 spikes/s), 24 generated a fast continuous firing pattern (> or = 2.5 spikes/s), and 6 cells displayed a bursting pattern of activity consisting of alternating periods of spike discharge and quiescence. None of the bursting cells exhibited regenerative endogenous potentials (plateau potentials). On the contrary, in four of these cells, the bursting activity was clearly due to patterned synaptic activity. 5. The cultured OT cells responded to exogenous gamma-aminobutyric acid (GABA) and muscimol with a hyperpolarization and an increase in membrane conductance. These effects still were observed in the presence of TTX, indicating that they were due to direct activation of GABA receptors in the cells. The GABA-induced response was mediated by GABAA receptors because it was blocked by bicuculline, but not by GABAB receptors, because baclofen and hydroxysaclofen had no effect on membrane potential and input resistance. 6. OT neurons responded to exogenous glutamate, quisqualate, and kainate with a depolarization concomitant with an increase in membrane conductance. N-methyl-D-aspartate depolarized the cells in Mg(2+)-free medium. These effects were observed in the presence of TTX, suggesting that OT cells expressed ionotropic glutamate receptors. Trans-(1S,3R)-1-amino-1,3-cyclopentane-dicarboxylic acid and (+/-)-alpha-amino-4-carboxymethylphenylglycine had no effect on OT cells, thus excluding the presence of metabotropic glutamate receptors. 7. Taken together, our observations demonstrate that hypothalamic slice cultures from 4- to 6-day-old rat neonates contain well-differentiated OT neurons that display electrical properties similar to those shown by adult neurons in vitro. Such cultures provide a reliable model to investigate membrane properties of adult OT neurons and a useful means to study the long-term modulation of their electrical behaviour by various agents known to affect OT cells in vivo.

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