Calcium-dependent chloride current induced by axotomy in rat sympathetic neurons. (original) (raw)
Related papers
Calcium currents in the normal adult rat sympathetic neurone
The Journal of Physiology, 1989
1. The calcium currents evoked by membrane depolarization in the mature and intact rat sympathetic neurone have been studied at 37 degrees C using two‐electrode voltage‐clamp analysis. 2. Under conditions that eliminate Na+ and K+ currents and 5 mM‐external Ca2+, inward currents were observed that activated at about ‐30 mV and reached maximum amplitude between 0 and +10 mV with time‐to‐peak values (2.7‐1.9 ms) decreasing with increasing membrane depolarization. Thereafter, calcium current (ICa) decayed to a virtually zero level with maintained depolarization. Two exponentials were required to describe the total inactivation process. The faster rate (tau = 29.3‐17.6 ms) is ten times the slower rate and proved to be only slightly voltage‐dependent. Double‐pulse experiments gave a similar time course of turn‐off. 3. No steady‐state inactivation was removed at holding potentials between ‐40 and ‐70 mV and indirect data suggest that all the ICa was available at ‐50 mV. Within the ‐30 to ...
Biochimica et Biophysica Acta (BBA) - Biomembranes, 1985
The relation of changes in internal, free Ca 2+, measured with arsenazo III, to the membrane potential, measured with the cyanine dye di-S-C2(5) or S6Rb+ distribution ratio, was studied in isolated guinea pig cortical nerve endings. Depolarization of the plasma membrane with veratridine or gramicidin as well as addition of ionophore A23187 led to an increase in cytosolic Ca 2+. Only the response to veratridine was inhibited by tetrodotoxin. The dependence of the depolarization-induced increase in intraterminal, free Ca 2+ on the membrane potential between about-50 to 0 mV was sigmoidal. A maximal increase in cytosolic Ca 2+ was reached when the membrane potential was depolarized from the resting level, about-64 mV, to about-40 mV. These results show that in isolated nerve endings the activation of voltage-sensitive Ca 2 + channels concomitantly leads to an increase in cytosolic, free Ca 2+. Comparison of the results of the present study with the previous electrophysiological observations indicate that Ca 2+ channels in synaptosomes, presynaptic nerve terminals of the squid giant synapse and cardiac cells have essentially similar voltage dependency.
Journal of Neurophysiology, 2003
Remarkable activity dependence was uncovered in the chloride conductance that operates in the subthreshold region of membrane potential, by using the two-microelectrode voltage-clamp technique in the mature and intact rat sympathetic neuron. Both direct and synaptic neuron tetanization (15 Hz, 10-s duration to saturate the response) resulted in a long-lasting (not less than 15 min) increase of cell input conductance (+70–150% 10 min after tetanus), accompanied by the onset of an inward current with the same time course. Both processes developed with similar properties in the postganglionic neuron when presynaptic stimulation was performed under current- or voltage-clamp conditions and were unaffected by external calcium on direct stimulation. The posttetanic effects were sustained by gCl increase because both conductance and current modifications were blocked by 0.5 mM Anthracene-9-carboxylic acid (a chloride channel blocker) but were unaffected by TEACl or cesium chloride treatment...
A Calcium-Dependent Chloride Current Increases Repetitive Firing in Mouse Sympathetic Neurons
Frontiers in physiology, 2018
Ca-activated ion channels shape membrane excitability in response to elevations in intracellular Ca. The most extensively studied Ca-sensitive ion channels are Ca-activated K channels, whereas the physiological importance of Ca-activated Cl channels has been poorly studied. Here we show that a Ca-activated Cl currents (CaCCs) modulate repetitive firing in mouse sympathetic ganglion cells. Electrophysiological recording of mouse sympathetic neurons in an preparation of the superior cervical ganglion (SCG) identifies neurons with two different firing patterns in response to long depolarizing current pulses (1 s). Neurons classified as phasic (Ph) made up 67% of the cell population whilst the remainders were tonic (T). When a high frequency train of spikes was induced by intracellular current injection, SCG sympathetic neurons reached an afterpotential mainly dependent on the ratio of activation of two Ca-dependent currents: the K [I] and CaCC. When the I was larger, an afterhyperpolar...
Participation of a Chloride Conductance in the Subthreshold Behavior of the Rat Sympathetic Neuron
Journal of Neurophysiology, 1999
The presence of a novel voltage-dependent chloride current, active in the subthreshold range of membrane potential, was detected in the mature and intact rat sympathetic neuron in vitro by using the two-microelectrode voltage-clamp technique. Hyperpolarizing voltage steps applied to a neuron held at −40/−50 mV elicited inward currents, whose initial magnitude displayed a linear instantaneous current-voltage ( I-V) relationship; afterward, the currents decayed exponentially with a single voltage-dependent time constant (63.5 s at −40 mV; 10.8 s at −130 mV). The cell input conductance decreased during the command step with the same time course as the current. On returning to the holding potential, the ensuing outward currents were accompanied by a slow increase in input conductance toward the initial values; the inward charge movement during the transient onresponse (a mean of 76 nC in 8 neurons stepped from −50 to −90 mV) was completely balanced by outward charge displacement during ...
The Journal of Physiology
1. Using the whole-cell recording mode of the patch-clamp technique, we have investigated kinetic and selectivity properties of a low-voltage-activated (l.v.a.) Ca2+ current in chick and rat dorsal root ganglion (d.r.g.) neurones. 2. L.v.a currents were activated at about-50 mV and reached maximum amplitudes between-30 and-20 mV with averages of-0-16 nA in chick and-03 nA in rat d.r.g. cells with 5 mM-extracellular Ca2+. Between-60 and-20 mV, the time to peak, tp, of this current decreased with increasing membrane depolarizations. An e-fold change of tp required a 14 mV potential change in chick and a 17 mV change in rat d.r.g. cells at 22 'C. 3. Between-50 and + 20 mV inactivation of this current was fast, single exponential and voltage dependent. In rat, the time constant of inactivation, Th, was smaller and less voltage dependent than in chick. 4. The amplitude of these currents increased by a factor of 5-10, when the extracellular Ca2+ concentration was changed from 1 to 95 mm. Amplitudes and kinetic parameters of the currents showed typical shifts along the voltage axis. No correlation between Ca2+ current amplitudes and activation-inactivation kinetics was found, suggesting that the reaction rates which control these processes are not dependent on Ca2+ entry. 5. Recovery from inactivation was voltage dependent and developed with a time constant, Tr' in the order of 1 s. Tr was nearly halved by changing the potential from-80 to-120 mV. 6. Tail currents associated with membrane repolarization were also voltage dependent and developed exponentially. Their time constant decreased by a factor of 3 when the potential was changed from-60 to-100 mV. 7. A second and more prominent Ca2+ current was activated at potentials positive to-20 mV (high-voltage-activated Ca2+ currents, h.v.a.), masking the time course of l.v.a. currents. Between-20 and 0 mV, time to peak of the entire current increased by a factor of 2 but decreased again at higher membrane potentials. Inactivation also became significantly slower in this potential range.
Two distinct Ca-dependent K currents in bullfrog sympathetic ganglion cells
Proceedings of the National Academy of Sciences
Healthy bullfrog sympathetic ganglion cells often show a two-component afterhyperpolarization (AHP). Both components can be reduced or abolished by adding Ca-channel blockers or by removing external Ca. Application of a single electrode "hybrid clamp"--i.e., switching from current- to voltage-clamp at the peak of the AHP, reveals that the slow AHP component is generated by a small, slow, monotonically decaying outward current, which we call IAHP. IAHP is blocked by Ca-removal or by apamin and is a pure K current. It is slightly sensitive to muscarine and to tetraethylammonium ion but is much less so than muscarine-sensitive (IM) and fast Ca-dependent (IC) K currents. It also can be recorded in dual-electrode voltage-clamp experiments, where it is seen as a slow, small component of the outward tail current that follows brief depolarizations to 0 mV or beyond. IC is seen as an early, fast, large component of the same tail current. Both components are blocked by Ca removal, b...
Potassium currents evoked by brief depolarizations in bull-frog sympathetic ganglion cells
The Journal of Physiology, 1987
1. Sympathetic neurones of the bullfrog Rana catesbeiana were subjected to a twoelectrode voltage-clamp technique in order to investigate the K+ currents which can be elicited by action potentials or similar brief depolarizations. 2. Four separate K+ currents were observed (Ic, IK' IAHP and IM)* These could be separated on the basis of voltage sensitivity, Ca2+ dependence and deactivation kinetics. 3. Two of these currents, which were clearly activated by an action potential, were Ca2+ dependent. A voltageand TEA (tetraethylammonium)-sensitive K+ current,