Ionic currents in crustacean neurosecretory cells

1990 ◽  
Vol 64 (5) ◽  
pp. 1514-1526 ◽  
Author(s):  
C. G. Onetti ◽  
U. Garcia ◽  
R. F. Valdiosera ◽  
H. Arechiga
Keyword(s):  
Voltage Clamp ◽  
Cell Voltage ◽  
Ionic Currents ◽  
Neurosecretory Cells ◽  
Negative Slope ◽  
Current Clamp ◽  
Outward Currents ◽  
Inward Currents ◽  
Cell Somata ◽  
Bursting Activity

1. The patterns of electrical activity and membrane characteristics of a population of neurosecretory-cell somata in the X-organ of the crayfish were investigated with microelectrodes and whole-cell, voltage-clamp techniques. Some neurons (56%) were silent but could be excited by intracellular current injection: other cells showed spontaneous tonic activity (35%), and some had spontaneous bursting activity (9%). The spiking activity was abolished by tetrodotoxin (TTX) exposure and by severing the axon near the cell body. After axotomy, only a small, slow, regenerative depolarization remained that could be blocked by Cd2+. 2. Under voltage clamp the steady-state I-V curve in low [Ca2+]i (9 X 10(-9) M) showed a slope conductance of 16.7 +/- 3.9 (SD) nS (n = 10) at -50 mV and zero current potential of -50.1 +/- 7.7 mV. In current-clamp mode these neurons were either silent or fired tonically. With high [Ca2+]i (1.7 X 10(-6) M) both the slope conductance and inward and outward currents were reduced. In some neurons high [Ca2+]i reveals a negative slope resistance in the range of -46 to -41 mV. It could be supressed by removing [Na+]o, but it was TTX insensitive. These are the neurons that under current clamp showed bursting activity. 3. The main inward current in cell somata was a Ca2+ current of 2 +/- 0.6 nA (n = 18), activated at -40 mV and peaking at 20 mV. It showed relaxation with prolonged pulses. No Na(+)-dependent, TTX-sensitive inward currents were recorded with short (100-ms) pulses in axotomized neurons. 4. Two outward currents could be distinguished.(ABSTRACT TRUNCATED AT 250 WORDS)

A voltage-clamp analysis of currents underlying cyclic AMP-induced membrane modulation in isolated peptidergic neurons of Aplysia

1984 ◽  
Vol 52 (2) ◽  
pp. 340-349 ◽  
Author(s):  
L. K. Kaczmarek ◽  
F. Strumwasser
Keyword(s):  
Cell Culture ◽  
Cyclic Amp ◽  
Voltage Clamp ◽  
Cultured Cells ◽  
Sodium Current ◽  
Negative Slope ◽  
Spontaneous Discharge ◽  
Inward Current ◽  
Outward Currents ◽  
Bag Cell Neurons

A variety of chemical and electrophysiological evidence indicates that the onset of afterdischarge and the subsequent profound enhancement of spike broadening that occur in the bag cell neurons of Aplysia are related to an increase in adenosine 3',5'-monophosphate-(cAMP) dependent protein phosphorylation. We have now used a two-electrode voltage clamp to study the properties of isolated bag cell neurons in cell culture and their response to 8 benzylthio-cAMP (8BTcAMP) and N6-n-butyl 8BTcAMP. These membrane-permeant and phosphodiesterase-resistant cAMP analogs induce spontaneous discharge and spike broadening in both the intact bag cell cluster and isolated bag cell neurons in cell culture. The dominant inward current in these cultured cells was found to be the calcium current, Ica, which was abolished by Co2+ (20 mM) or Ni2+ (10 mM) and could be observed in Na+-free media. In a minority of cells (2 of 12), in normal ionic media, a transient inward current was observed that was unaffected by Co2+ and Ni2+ and probably represents a sodium current. The three characterized potassium currents, the delayed rectifying current IK, the calcium-dependent current IC, and the early transient current IA, distinguished by their differing pharmacological and voltage-activation properties, were present in all healthy cells. Three effects of the cyclic AMP analogs (0.5 mM) on the electrical properties of these cells were 1) the emergence of a region of negative slope resistance in the steady-state I-V relations, 2) a depression of the net sustained outward currents due to depolarizing commands, and 3) a marked reduction in IA. When outward currents had been largely suppressed using high concentrations of tetraethylammonium (TEA) ions (100-460 mM) no effects of the cyclic AMP analogs could be observed on peak inward currents using NA+ and Ca2+ or Ba2+ as carriers of inward current. At least part of these electrical effects of the cyclic AMP analogs could be accounted for by a depression of a delayed potassium current and the A current.

Muscarinic modulation of GABAergic transmission to neurons in the rat subfornical organ

2001 ◽  
Vol 280 (6) ◽  
pp. R1657-R1664 ◽  
Author(s):  
Sheng-Hong Xu ◽  
Eiko Honda ◽  
Kentaro Ono ◽  
Kiyotoshi Inenaga
Keyword(s):  
Muscarinic Receptors ◽  
Reversal Potential ◽  
Cell Voltage ◽  
Gaba Release ◽  
Postsynaptic Membrane ◽  
Subfornical Organ ◽  
Dependent Manner ◽  
Current Clamp ◽  
Inward Currents ◽  
Frequency Of Action Potentials

Cholinergic actions on subfornical organ (SFO) neurons in rat slice preparations were studied by using whole cell voltage- and current-clamp recordings. In the voltage-clamp recordings, carbachol and muscarine decreased the frequency of GABAergic inhibitory postsynaptic currents (IPSCs) in a dose-dependent manner, with no effect on the amplitudes or the time constants of miniature IPSCs. Meanwhile, carbachol did not influence the amplitude of the outward currents induced by GABA. Furthermore, carbachol and muscarine also elicited inward currents in a TTX-containing solution. From the current-voltage relationship, the reversal potential was estimated to be −7.1 mV. These carbachol-induced responses were antagonized by atropine. In the current-clamp recordings, carbachol depolarized the membrane with increased frequency of action potentials. These observations suggest that acetylcholine suppresses GABA release through muscarinic receptors located on the presynaptic terminals. Acetylcholine also directly affects the postsynaptic membrane through muscarinic receptors, by opening nonselective cation channels. A combination of these presynaptic and postsynaptic actions may enhance activation of SFO neurons by acetylcholine.

Dopamine modulates the slow Ca(2+)-activated K+ current IAHP via cyclic AMP-dependent protein kinase in hippocampal neurons

1995 ◽  
Vol 74 (6) ◽  
pp. 2749-2753 ◽  
Author(s):  
P. Pedarzani ◽  
J. F. Storm
Keyword(s):  
Protein Kinase ◽  
Voltage Clamp ◽  
Cell Voltage ◽  
Spike Frequency ◽  
Receptor Type ◽  
Spike Frequency Adaptation ◽  
Current Clamp ◽  
Whole Cell ◽  
Frequency Adaptation ◽  
K Current

1. The effects of dopamine on the slow Ca(2+)-dependent K+ current (IAHP; AHP, afterhyperpolarization) and spike frequency adaptation were studied by whole cell voltage-clamp and sharp microelectrode current-clamp recordings in rat CA1 pyramidal neurons in rat hippocampal slices. 2. Dopamine suppressed IAHP in a dose-dependent manner, under whole cell voltage-clamp conditions. Similarly, under current-clamp conditions, dopamine inhibited spike frequency adaptation and suppressed the slow afterhyperpolarization. 3. The effect of dopamine on IAHP was mimicked by a D1 receptor agonist and blocked by dopamine receptor antagonists only in a minority of the cells. 4. Dopamine suppressed IAHP after blocking or desensitizing the beta-adrenergic receptors and, hence, did not act by cross-reacting with this receptor type. 5. The effects of dopamine on IAHP and spike frequency adaptation were suppressed by blocking the adenosine 3',5'-cyclic monophosphate (cAMP)-dependent kinase (PKA) with Rp-cAMPS and, hence, are probably mediated by the activation of this kinase. 6. We conclude that dopamine increases hippocampal neuron excitability, like other monoamine neurotransmitters, by suppressing IAHP and spike frequency adaptation, via cAMP and protein kinase A. The receptor type mediating this effect of dopamine remains to be defined.

Characterization of Ionic Currents in Peptidergic Neurons from Eyestalks of Chinese Mitten Crab Eriocheir sinensis

2011 ◽  
Vol 108 ◽  
pp. 116-120
Author(s):  
Jin Sheng Sun ◽  
Li Ping Wang ◽  
Xu Yun Geng
Keyword(s):  
Ionic Current ◽  
Ionic Currents ◽  
Eriocheir Sinensis ◽  
Neurosecretory Cells ◽  
Transient Current ◽  
Peptidergic Neurons ◽  
Chinese Mitten Crab ◽  
Patch Clamp Technique ◽  
Outward Currents ◽  
Mitten Crab

The Whole-cell patch clamp technique was used to study the properties of voltage dependent ion channel expressed by the cultured types A、B、C neurosecretory cells dissociated from medulla terminalis X-organ (MTXO) of Chinese mitten crab Eriocheir sinensis 24-48 hours after plating. Under voltage clamp conditions, significantly inward currents were recorded from all three kinds of neurons, followed by large outward currents. When outward currents were suppressed with use of 3mmol/L 4-aminopyridine (4-AP) and 30mmol/L tetraethylammonium (TEA), a tetrodotoxin-sensitive Na+ current （INa） and a slow (time to peak current 6~8mS at +10mV), Cd2+-sensitive Ca2+ current (ICa) were resolved. INa was activated at potential-40mV and was maximal at-10mV. In TTX, ICa was activated at potential-30mV, was maximal at 10~20mV. In the presence of 1mol/L TTX and 0.5mmol/L Cd2+, a 4-AP-sensitive transient current and a slower-rising, TEA-sensitive current were recorded from a holding potential of-50mV. On the basis of electric feature and pharmacology, transient current was identified as IA, and late, slower-rising current as IK. IA and IK showed the same activation threshold of-30mV. In conclusion, no differences were observed on the properties and kinetics of ionic current among the three kinds of neurons. By comparison with those described in crab Cardisoma carnifex and crayfish Procambarus clarkia, there existed diversity of excitability in X-organ peptidergic neurons from different crustaceans.

scholarly journals Frequency dependent responses of neuronal models to oscillatory inputs in current versus voltage clamp

2019 ◽  
Author(s):  
Horacio G. Rotstein ◽  
Farzan Nadim
Keyword(s):  
Membrane Potential ◽  
Voltage Clamp ◽  
Measurement Techniques ◽  
Ionic Currents ◽  
Inactivation Kinetics ◽  
Current Clamp ◽  
Cellular Mechanisms ◽  
Sinusoidal Input ◽  
Two Measures ◽  
Sinusoidal Current

AbstractAction potential generation in neuron depends on a membrane potential threshold, and therefore on how subthreshold inputs influence this voltage. In oscillatory networks, for example, many neuron types have been shown to produce membrane potential (Vm) resonance: a maximum subthreshold response at a nonzero frequency. Resonance is usually measured by recording Vm in response to a sinusoidal current (Iapp), applied at different frequencies (f), an experimental setting known as current clamp (I-clamp). Several recent studies, however, use the voltage clamp (V-clamp) method to control Vm with a sinusoidal input at different frequencies (Vapp(f)) and measure the total membrane current (Im). The two methods obey systems of differential equations of different dimensionality and, while I-clamp provides a measure of electrical impedance (Z(f) = Vm(f)/Iapp(f)), V-clamp measures admittance (Y (f) = Im(f)/Vapp(f)). We analyze the relationship between these two measurement techniques. We show that, despite different dimensionality, in linear systems the two measures are equivalent: Z = Y−1. However, nonlinear model neurons produce different values for Z and Y−1. In particular, nonlinearities in the voltage equation produce a much larger difference between these two quantities than those in equations of recovery variables that describe activation and inactivation kinetics. Neurons are inherently nonlinear and, notably, with ionic currents that amplify resonance, the voltage clamp technique severely underestimates the current clamp response. We demonstrate this difference experimentally using the PD neurons in the crab stomatogastric ganglion. These findings are instructive for researchers who explore cellular mechanisms of neuronal oscillations.

scholarly journals Large-Conductance Calcium-Activated Potassium Channels and Voltage-Dependent Sodium Channels in Human Cementoblasts

2021 ◽  
Vol 12 ◽  
Author(s):  
Satomi Kamata ◽  
Maki Kimura ◽  
Sadao Ohyama ◽  
Shuichiro Yamashita ◽  
Yoshiyuki Shibukawa
Keyword(s):  
Alveolar Bone ◽  
Attachment Site ◽  
Ionic Currents ◽  
Ionic Channels ◽  
Patch Clamp Recording ◽  
Physiological Processes ◽  
Whole Cell Patch Clamp ◽  
Outward Currents ◽  
Voltage Dependent ◽  
Inward Currents

Cementum, which is excreted by cementoblasts, provides an attachment site for collagen fibers that connect to the alveolar bone and fix the teeth into the alveolar sockets. Transmembrane ionic signaling, associated with ionic transporters, regulate various physiological processes in a wide variety of cells. However, the properties of the signals generated by plasma membrane ionic channels in cementoblasts have not yet been described in detail. We investigated the biophysical and pharmacological properties of ion channels expressed in human cementoblast (HCEM) cell lines by measuring ionic currents using conventional whole-cell patch-clamp recording. The application of depolarizing voltage steps in 10 mV increments from a holding potential (Vh) of −70 mV evoked outwardly rectifying currents at positive potentials. When intracellular K+ was substituted with an equimolar concentration of Cs+, the outward currents almost disappeared. Using tail current analysis, the contributions of both K+ and background Na+ permeabilities were estimated for the outward currents. Extracellular application of tetraethylammonium chloride (TEA) and iberiotoxin (IbTX) reduced the densities of the outward currents significantly and reversibly, whereas apamin and TRAM-34 had no effect. When the Vh was changed to −100 mV, we observed voltage-dependent inward currents in 30% of the recorded cells. These results suggest that HCEM express TEA- and IbTX-sensitive large-conductance Ca2+-activated K+ channels and voltage-dependent Na+ channels.

scholarly journals A balance of outward and linear inward ionic currents is required for the generation of slow wave oscillations

2017 ◽  
Author(s):  
Jorge Golowasch ◽  
Amitabha Bose ◽  
Yinzheng Guan ◽  
Dalia Salloum ◽  
Andrea Roeser ◽  
...  
Keyword(s):  
Outward Current ◽  
Ionic Currents ◽  
Oscillatory Activity ◽  
Negative Slope ◽  
High Threshold ◽  
Dynamic Clamp ◽  
Cancer Borealis ◽  
Slow Oscillations ◽  
Pyloric Network ◽  
Inward Currents

AbstractRegenerative inward currents help produce slow oscillations through a negative-slope conductance region of their current-voltage relationship that is well approximated by a linear negative conductance. We used dynamic clamp injections of a linear current with this conductance, INL, to explore why some neurons can generate intrinsic slow oscillations whereas others cannot. We addressed this question, in synaptically isolated neurons of the crab Cancer borealis, after blocking action potentials. The pyloric network consists of distinct pacemaker group and follower neurons, all of which express the same complement of ionic currents. When the pyloric dilator (PD) neuron, a member of the pacemaker group, was injected with INL using dynamic clamp, it consistently produced slow oscillations. In contrast, the lateral pyloric (LP) or ventral pyloric (VD) follower neurons, failed to oscillate with INL. To understand these distinct behaviors, we compared outward current levels of PD, LP and VD neurons. We found that LP and VD neurons had significantly larger high-threshold potassium currents (IHTK) than PD, and LP had lower transient potassium current, IA. Reducing IHTK pharmacologically enabled both LP and VD neurons to produce oscillations with INL, whereas modifying IA levels did not affect INL-induced oscillations. Using phase-plane and bifurcation analysis of a simplified model cell, we demonstrate that large levels of IHTK can block INL-induced oscillatory activity, whereas generation of oscillations is almost independent of IA levels. These results demonstrate the importance of a balance between inward pacemaking currents and high-threshold K+current levels in determining slow oscillatory activity.

Ionic currents in identified swimmeret motor neurones of the crayfish Pacifastacus leniusculus

1995 ◽  
Vol 198 (7) ◽  
pp. 1483-1492 ◽  
Author(s):  
A Chrachri
Keyword(s):  
Time Course ◽  
Outward Current ◽  
Rhythmic Activity ◽  
Ionic Currents ◽  
Power Stroke ◽  
Transient Outward Current ◽  
Patch Clamp Technique ◽  
Outward Currents ◽  
Inward Currents ◽  
Motor Neurones

Ionic currents from freshly isolated and identified swimmeret motor neurones were characterized using a whole-cell patch-clamp technique. Two outward currents could be distinguished. A transient outward current was elicited by delivering depolarizing voltage steps from a holding potential of -80 mV. This current was inactivated by holding the cells at a potential of -40 mV and was also blocked completely by 4-aminopyridine. A second current had a sustained time course and continued to be activated at a holding potential of -40 mV. This current was partially blocked by tetraethylammonium. These outward currents resembled two previously described potassium currents: the K+ A-current and the delayed K+ rectifier current respectively. Two inward currents were also detected. A fast transient current was blocked by tetrodotoxin and inactivated at holding potential of -40 mV, suggesting that this is an inward Na+ current. A second inward current had a sustained time course and was affected neither by tetrodotoxin nor by holding the cell at a potential of -40 mV. This current was substantially enhanced by the addition of Ba2+ to the bath or when equimolar Ba2+ replaced Ca2+ as the charge carrier. Furthermore, this current was significantly suppressed by nifedipine. All these points suggest that this is an L-type Ca2+ current. Bath application of nifedipine into an isolated swimmeret preparation affected both the frequency of the swimmeret rhythm and the duration of power-stroke activity, suggesting an important role for the inward Ca2+ current in maintaining a regular swimmeret rhythmic activity in crayfish.

Active Dendritic Membrane Properties of XenopusLarval Spinal Neurons Analyzed With a Whole Cell Soma Voltage Clamp

2000 ◽  
Vol 83 (3) ◽  
pp. 1381-1393 ◽  
Author(s):  
Benoit Saint Mleux ◽  
L. E. Moore
Keyword(s):  
Action Potential ◽  
Frequency Domain ◽  
Voltage Clamp ◽  
Membrane Potentials ◽  
Calcium Currents ◽  
Membrane Properties ◽  
Constant Current ◽  
Negative Slope ◽  
Spinal Neurons ◽  
Current Clamp

Voltage- and current-clamp measurements of inwardly directed currents were made from the somatic regions of Xenopus laevisspinal neurons. Current-voltage ( I-V) curves determined under voltage clamp, but not current clamp, were able to indicate a negative slope conductance in neurons that showed strong accommodating action potential responses to a constant current stimulation. Voltage-clamp I-V curves from repetitive firing neurons did not have a net negative slope conductance and had identical I-V plots under current clamp. Frequency domain responses indicate negative slope conductances with different properties with or without tetrodotoxin, suggesting that both sodium and calcium currents are present in these spinal neurons. The currents obtained from a voltage clamp of the somatic region were analyzed in terms of spatially controlled soma membrane currents and additional currents from dendritic potential responses. Linearized frequency domain analysis in combination with both voltage- and current-clamp responses over a range of membrane potentials was essential for an accurate determination of consistent neuronal model behavior. In essence, the data obtained at resting or hyperpolarized membrane potentials in the frequency domain were used to determine the electrotonic structure, while both the frequency and time domain data at depolarized potentials were required to characterize the voltage-dependent channels. Finally, the dendritic and somatic membrane properties were used to reconstruct the action potential behavior and quantitatively predict the dependence of neuronal firing properties on electrotonic structure. The reconstructed action potentials reproduced the behavior of two broad distributions of interneurons characterized by their degree of accommodation. These studies suggest that in addition to the ionic conductances, electrotonic structure is correlated with the action potential behavior of larval neurons.

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