N-Methyl-d-Aspartate–Induced Oscillations in Whole Cell Clamped Neurons From the Isolated Spinal Cord of Xenopus laevis Embryos

1999 ◽  
Vol 82 (2) ◽  
pp. 1069-1073 ◽  
Author(s):  
L. Prime ◽  
Y. Pichon ◽  
L. E. Moore
Keyword(s):  
Spinal Cord ◽  
Low Frequency ◽  
Oscillatory Activity ◽  
Patch Clamp Technique ◽  
Whole Cell ◽  
Voltage Dependent ◽  
Whole Cell Recordings ◽  
External Calcium ◽  
Xenopus Laevis Embryos ◽  
Embryonic Neurons

The patch-clamp technique was used to measure the effect of N-methyl-d-aspartate (NMDA) on Xenopus embryonic neurons in an isolated, but intact spinal cord. Whole cell recordings were done at external calcium concentrations of 1 mM. NMDA alone (50–200 μM) or in association with 10 μM serotonin or glycine induced oscillatory activity in most presumed motoneurons, which were therefore considered part of rhythm generating networks. In the presence of TTX, one-half of these neurons maintained this activity. The oscillations fell into two main categories: voltage-dependent, low-frequency (0.3–0.5 Hz) and voltage-independent, high-frequency (3–8 Hz) oscillations. NMDA alone induced TTX-insensitive oscillations in one-third of the neurons; however, the percentage of neurons showing oscillations was greater in the presence of exogenous 5-hydroxytryptamine (5-HT) or glycine. Because these observations were made at embryonic stages where little or no serotonergic innervation exists, it is likely that NMDA-induced intrinsic oscillatory activity in Xenopus embryonic neurons does not require 5-HT.

scholarly journals Slow inactivation of L-type calcium current distorts the measurement of L- and T-type calcium current in Purkinje myocytes.

1993 ◽  
Vol 102 (5) ◽  
pp. 859-869 ◽  
Author(s):  
N B Datyner ◽  
I S Cohen
Keyword(s):  
Patch Clamp ◽  
Calcium Current ◽  
Slow Inactivation ◽  
Total Calcium ◽  
Patch Clamp Technique ◽  
Whole Cell ◽  
Whole Cell Patch Clamp ◽  
Voltage Curve ◽  
Voltage Dependent ◽  
Method Of Measurement

We have examined slow inactivation of L-type calcium current in canine Purkinje myocytes with the whole cell patch clamp technique. Slow inactivation is voltage dependent. It is negligible at -50 mV but can inactivate more than half of available iCaL at -10 mV. There are two major consequences of this slow inactivation. First, standard protocols for the measurement of T-type current can dramatically overestimate its contribution to total calcium current, and second, the position and steepness of the inactivation versus voltage curve for iCaL will depend on the method of measurement. Given the widespread attempts to identify calcium current components and characterize them biophysically, an important first step should be to determine the extent of slow inactivation of calcium current in each preparation.

The development of voltege-dependent ionic conductances In murine spinal cord neurones in culture

1988 ◽  
Vol 66 (10) ◽  
pp. 1328-1336 ◽  
Author(s):  
C. Krieger ◽  
T. A. Sears
Keyword(s):  
Spinal Cord ◽  
Sodium Current ◽  
Potassium Conductance ◽  
Calcium Currents ◽  
Delayed Rectifier ◽  
Patch Clamp Technique ◽  
Calcium Dependent ◽  
Ionic Conductances ◽  
Voltage Dependent

The development of voltage-dependent ionic conductances of foetal mouse spinal cord neurones was examined using the whole-cell patch-clamp technique on neurones cultured from embryos aged 10–12 days (E10–E12) which were studied between the first day in vitro (V1) to V10. A delayed rectifier potassium conductance (IK) and a leak conductance were observed in neurones of E10.V1, E11, V1, and E12, V1 as well as in neurones cultured for longer periods. A rapidly activating and inactivating potassium conductance (IA) was seen in neurones from E11, V2 and E12, V1 and at longer times in vitro. A tetrodotoxin (TTX) sensitive sodium-dependent inward current was observed in neurones of E11 and E12 from V1 onwards. Calcium-dependent conductances were not detectable in these neurones unless the external calcium concentration was raised 10- to 20-foid and potassium conductances were blocked. Under these conditions calcium currents could be observed as early as E11, V3 and E12, V2 and at subsequent times in vitro. The pattern of development of voltage-dependent ionic conductances in murine spinal neurones is such that initially leak and potassium currents are present followed by sodium current and subsequently calcium current.

scholarly journals Use Dependent Attenuation of Rat HCN1-Mediated Ih in Intact HEK293 Cells

2016 ◽  
Vol 38 (6) ◽  
pp. 2079-2093 ◽  
Author(s):  
Lennart Barthel ◽  
Olivia Reetz ◽  
Ulf Strauss
Keyword(s):  
Mammalian Cells ◽  
Hek293 Cells ◽  
Hcn Channels ◽  
Patch Clamp Technique ◽  
Intact Cells ◽  
Whole Cell ◽  
Human Embryonic Kidney Cells ◽  
Intracellular Content ◽  
Voltage Dependent ◽  
Activity Dependence

Background/Aims: Cationic currents (Ih) through the fast activating and relatively cAMP insensitive subtype of hyperpolarization-activated cyclic nucleotide-gated (HCN) channels, HCN1, are limited by cytosolic factors in mammalian cells. This cytosolic HCN1 break is boosted by changes in membrane voltage that are not characterized on a biophysical level, yet. Methods: We overexpressed rat (r)HCN1 in human embryonic kidney cells (HEK293) and recorded pharmacologically isolated Ih in cell-attached or whole-cell mode of the patch-clamp technique. Results: Recurring activation of rHCN1 reduced and slowed Ih in intact HEK293 cells (cell-attached mode). On the contrary, sustained disruption of the intracellular content (whole-cell mode) ceased activity dependence and partially enables voltage dependent hysteresis. The activity induced Ih attenuation in intact cells was independent of the main external cation, depended on the number of previous forced activations and was - at least in part - due to a shift in the voltage dependence of activation towards hyperpolarization as estimated by an adapted tail current analysis. Intracellular elevation of cAMP could not reverse the changes in Ih. Conclusion: Reduction of rHCN1 mediated Ih is use dependent and may involve the coupling of voltage sensor and pore.

Modulation by endogenously released ATP and opioids of chromaffin cell calcium channels in mouse adrenal slices

2011 ◽  
Vol 300 (3) ◽  
pp. C610-C623 ◽  
Author(s):  
A. Hernández ◽  
P. Segura-Chama ◽  
N. Jiménez ◽  
A. G. García ◽  
J. M. Hernández-Guijo ◽  
...  
Keyword(s):  
Calcium Channels ◽  
Chromaffin Cells ◽  
Opiate Receptors ◽  
Tonic Inhibition ◽  
Inactivation Kinetics ◽  
High Threshold ◽  
Patch Clamp Technique ◽  
Whole Cell ◽  
Voltage Dependent ◽  
Patch Configuration

Modulation of high-threshold voltage-dependent calcium channels by neurotransmitters has been the subject of numerous studies in cultures of neurons and chromaffin cells. However, no studies on such modulation exist in chromaffin cells in their natural environment, the intact adrenal medullary tissue. Here we performed such a study in voltage-clamped chromaffin cells of freshly prepared mouse adrenal slices under the whole cell configuration of the patch-clamp technique. The subcomponents of the whole cell inward Ca2+ current ( ICa) accounted for 49% for L-, 28% for N-, and 36% for P/Q-type channels. T-type Ca2+ channels or residual R-type Ca2+ currents were not seen. However, under the perforated-patch configuration, 20% of ICa accounted for a toxin-resistant R-type Ca2+ current. Exogenously applied ATP and methionine-enkephalin (Met-enk) inhibited ICa by 33%. Stop-flow and Ca2+ replacement by Ba2+, which favored the release of endogenous ATP and opioids, also inhibited ICa, with no changes in activation or inactivation kinetics. This inhibition was partially voltage independent and insensitive to prepulse facilitation. Furthermore, in about half of the cells, suramin and naloxone augmented ICa in the absence of exogenous application of ATP/Met-enk. No additional modulation of ICa was obtained after bath application of exogenous ATP and opioids to these already inhibited cells. Augmentation of ICa was also seen upon intracellular dialysis of guanosine 5′-[β-thio]diphosphate (GDPβS), indicating the existence in the intact slice of a tonic inhibition of ICa in resting conditions. These results suggest that in the intact adrenal tissue a tonic inhibition of ICa exists, mediated by purinergic and opiate receptors.

scholarly journals Thalamic circuitry and thalamocortical synchrony

2002 ◽  
Vol 357 (1428) ◽  
pp. 1659-1673 ◽  
Author(s):  
Edward G. Jones
Keyword(s):  
Cortical Neurons ◽  
Low Frequency ◽  
Oscillatory Activity ◽  
Reticular Nucleus ◽  
Cortical Cells ◽  
Dorsal Thalamus ◽  
High Frequency Oscillations ◽  
Voltage Dependent ◽  
Layer V ◽  
Layer Vi

The corticothalamic system has an important role in synchronizing the activities of thalamic and cortical neurons. Numerically, its synapses dominate the inputs to relay cells and to the γ–amino butyric acid (GABA)ergic cells of the reticular nucleus (RTN). The capacity of relay neurons to operate in different voltage–dependent functional modes determines that the inputs from the cortex have the capacity directly to excite the relay cells, or indirectly to inhibit them via the RTN, serving to synchronize high– or low–frequency oscillatory activity respectively in the thalamocorticothalamic network. Differences in the α–amino–3–hydroxy–5–methyl–4–isoxazolepropionic acid (AMPA) subunit composition of receptors at synapses formed by branches of the same corticothalamic axon in the RTN and dorsal thalamus are an important element in the capacity of the cortex to synchronize low–frequency oscillations in the network. Interactions of focused corticothalamic axons arising from layer VI cortical cells and diffuse corticothalamic axons arising from layer V cortical cells, with the specifically projecting core relay cells and diffusely projecting matrix cells of the dorsal thalamus, form a substrate for synchronization of widespread populations of cortical and thalamic cells during high–frequency oscillations that underlie discrete conscious events.

scholarly journals Facilitation of Somatic Calcium Channels Can Evoke Prolonged Tail Currents in Rat Hypoglossal Motoneurons

2007 ◽  
Vol 98 (2) ◽  
pp. 1042-1047 ◽  
Author(s):  
Anna T. Moritz ◽  
Gregory Newkirk ◽  
Randall K. Powers ◽  
Marc D. Binder
Keyword(s):  
Voltage Clamp ◽  
Calcium Currents ◽  
Whole Cell ◽  
Persistent Inward Currents ◽  
Hypoglossal Motoneurons ◽  
Pharmacological Tests ◽  
Voltage Ramp ◽  
Voltage Dependent ◽  
Inward Currents ◽  
Whole Cell Recordings

Voltage-dependent persistent inward currents (PICs) make an important contribution to the input-output properties of alpha motoneurons. PICs are thought to be mediated by membrane channels located primarily on the dendrites as evidenced by prolonged tail currents following the termination of a voltage step and by a clockwise hysteresis in the whole cell inward currents recorded in response to depolarizing then repolarizing voltage ramp commands. We report here, however, that voltage-clamp currents with these same features can be generated in isolated somatic membrane patches from rat hypoglossal motoneurons. Long-lasting (200–800 ms) tail currents after 1-s voltage-clamp pulses were observed in nucleated patches from 16 of 23 cells. Further, these somatic PICs display “facilitation” in response to conditioning depolarization as previously observed in whole cell recordings from intact neurons. Pharmacological tests suggest that the PICs were primarily mediated by Cav1 channels. Our results show that many of the features of persistent calcium currents recorded from intact motoneurons do not necessarily reflect a remote dendritic origin but can also be ascribed to the intrinsic properties of their Cav1 channels.

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