Development of ionic conductances in neurons of neurons of the inferior olive in the rat: an in vitro study

1988 ◽  
Vol 234 (1275) ◽  
pp. 199-218 ◽  
Keyword(s):  
Membrane Potential ◽  
Inferior Olive ◽  
Early Period ◽  
In Vitro Study ◽  
Inward Rectification ◽  
High Threshold ◽  
Ca Channel ◽  
Ionic Conductances ◽  
Low Threshold

Neurons of the inferior olive of the rat were studied at different stages of their postnatal (PN) development by using the current clamp technique in slices maintained in vitro . Antidromic and synaptic activation of inferior olivary neurons could be achieved in preparations as young as PN day 2. Neurons at this age already exhibited a variety of ionic conductances which included fast sodium-dependent spikes, high-threshold and low-threshold calcium spikes, potassium-dependent currents, Ca-dependent after-hyperpolarizing potentials (AHPS), and both instan­taneous and time-dependent inward rectification at hyperpolarized levels of membrane potential. The two types of Ca-dependent responses recorded in olivary neurons during the first postnatal week were graded with the magnitude of the depolarization imposed on the cells. Further­more, the high-threshold Ca spikes were only clearly observed during this early period when K conductances were depressed by the injection of caesium into the cells or by bath application of 4-aminopyridine. In contrast, the high-threshold Ca spikes could be obtained without sup­pression of K currents and were all-or-none in character in some neurons after PN day 8 and in all neurons after PN day 11. The observations suggest that the balance between K and Ca currents changes throughout maturation and is largely in favour of the K current until about the end of the first PN week. At all ages studied, the low-threshold Ca spikes were much less sensitive to the Ca channel blocker cadmium than were the high-threshold Ca spikes. Finally, spontaneous, regular oscillations of the membrane potential were observed for the first time at PN day 16 and were only commonly observed after PN day 19, suggesting a late develop­ment of electrotonic coupling between olivary neurons.

Electrophysiological properties of neurons in the lateral habenula nucleus: an in vitro study

1988 ◽  
Vol 59 (1) ◽  
pp. 212-225 ◽  
Author(s):  
K. S. Wilcox ◽  
M. J. Gutnick ◽  
G. R. Christoph
Keyword(s):  
Membrane Potential ◽  
Action Potentials ◽  
In Vitro Study ◽  
Input Resistance ◽  
Membrane Potentials ◽  
Resting Membrane Potential ◽  
Lateral Habenula ◽  
Low Threshold ◽  
The Mean

1. The electroresponsive characteristics of neurons in the lateral habenula were studied with intracellular recordings in a brain slice preparation of guinea pig diencephalon maintained in vitro. One hundred and two neurons met the criteria for recording stability, and of these, 18 were analyzed in detail. For these 18 neurons, the mean resting membrane potential was -61.9 mV, the mean input resistance was 124 M omega, and the mean spike amplitude of fast action potentials was 60.3 mV. 2. Lateral habenula neurons were found to have distinct patterns of activity dependent on membrane potential. At membrane potentials more positive than -65 mV, depolarization elicited trains of sodium-dependent fast action potentials. At membrane potentials more negative than -65 mV, slight depolarization elicited a tetrodotoxin-insensitive wave of depolarization, called a low-threshold spike (LTS), from which a burst of fast action potentials were triggered. The principal conductance underlying the LTS is a low-threshold calcium conductance, which is inactivated at membrane potential more positive than -65 mV and deinactivated when the membrane is hyperpolarized to potentials more negative than -65 V. 3. Upon termination of injected hyperpolarizing current, many neurons displayed oscillation in membrane potential at a frequency of 3–10 Hz, thereby generating repetitive bursts of fast spikes. 4. The pattern of neuronal activity in lateral habenula neurons was highly sensitive to slight alterations in membrane potential. The ability of these neurons to fire action potentials in two modes, tonically and in bursts, and the propensity of these neurons to dramatically alter their output in response to transient hyperpolarizing input, indicate that transmission through this relay in the dorsal diencephalic conduction system may be greatly augmented by relatively small hyperpolarizing influences on the individual neurons.

Intrinsic Properties Shape the Firing Pattern of Ventral Horn Interneurons From the Spinal Cord of the Adult Turtle

2006 ◽  
Vol 96 (5) ◽  
pp. 2670-2677 ◽  
Author(s):  
Morten Smith ◽  
Jean-François Perrier
Keyword(s):  
Spinal Cord ◽  
Activity Patterns ◽  
Ventral Horn ◽  
Inward Rectification ◽  
Intrinsic Properties ◽  
Patch Clamp Technique ◽  
Firing Patterns ◽  
Pharmacological Tests ◽  
Low Threshold

Interneurons in the ventral horn of the spinal cord play a central role in motor control. In adult vertebrates, their intrinsic properties are poorly described because of the lack of in vitro preparations from the spinal cord of mature mammals. Taking advantage of the high resistance to anoxia in the adult turtle, we used a slice preparation from the spinal cord. We used the whole cell blind patch-clamp technique to record from ventral horn interneurons. We characterized their firing patterns in response to depolarizing current pulses and found that all the interneurons fired repetitively. They displayed bursting, adapting, delayed, accelerating, or oscillating firing patterns. By combining electrophysiological and pharmacological tests, we showed that interneurons expressed slow inward rectification, plateau potential, voltage-sensitive transient outward rectification, and low-threshold spikes. These results demonstrate a diversity of intrinsic properties that may enable a rich repertoire of activity patterns in the network of ventral horn interneurons.

Differential electroresponsiveness of stellate and pyramidal-like cells of medial entorhinal cortex layer II

1993 ◽  
Vol 70 (1) ◽  
pp. 128-143 ◽  
Author(s):  
A. Alonso ◽  
R. Klink
Keyword(s):  
Membrane Potential ◽  
Entorhinal Cortex ◽  
Morphological Characteristics ◽  
Oscillatory Activity ◽  
Inward Rectification ◽  
Projection Neurons ◽  
Medial Entorhinal Cortex ◽  
Mean Frequency ◽  
Subthreshold Oscillations

1. The electroresponsive properties of neurons from layer II of the rat medial entorhinal cortex (MEC) were studied by intracellular recording under current clamp in an in vitro brain slice preparation. From a total of 184 cells that fulfilled our criteria for recording stability, two groups of projection neurons were distinguished on the basis of their intrinsic biophysical properties and morphological characteristics (demonstrated by intracellular biocytin injection; n = 34). 2. Stellate cells (SCs) were the most abundant (69%). They were highly electroresponsive, and minimal changes (1-3 mV) of membrane potential generated an active response. Subthreshold depolarizing or hyperpolarizing current pulse injection always caused the membrane potential to attain an early peak and then sag to a lower level. Depolarization-induced "sags" were larger and determined early firing in all cells. The voltage-current relationship of SCs was markedly non-linear, demonstrating robust inward rectification in the hyperpolarizing and depolarizing range. 3. SCs generated persistent rhythmic subthreshold voltage oscillations on DC depolarization positive to -60 mV. The mean frequency of the oscillations was 8.6 Hz (theta range) at a membrane potential of approximately -55 mV, at which level occasional single spiking also occurred. At slightly more positive potentials, a striking 1- to 3-Hz repetitive bursting pattern emerged. This consisted of nonadapting trains of spikes ("clusters") interspersed with subthreshold oscillations that had a mean frequency of 21.7 Hz (beta range). 4. Nonstellate cells (39%; mostly pyramidal-like) displayed time-dependent inward rectification that was less pronounced than that of SCs, and minimal depolarization-induced sags. On threshold depolarization, firing was always preceded by a slowly rising ramp depolarization and thus occurred with a long delay. Inward rectification in the depolarizing range was very pronounced. However, non-SCs did not generate persistent rhythmic subthreshold oscillatory activity or spike clusters. 5. Of the electrophysiological parameters quantified, spike threshold, spike duration, depolarizing afterpotential amplitude and apparent membrane time constant demonstrated statistically significant differences between SCs and non-SCs. 6. The repetitive hiring properties in response to square current pulses of short duration (< 500 ms) were also different between SCs and non-SCs. First, most SCs displayed a bilinear frequency-current (f-I) relationship for only the first interspike interval, whereas most non-SCs displayed a bilinear relationship for all intervals. Second, SCs had a much steeper primary f-I slope for early intervals than non-SCs. Finally, SCs displayed more pronounced and faster spike frequency adaptation than non-SCs.(ABSTRACT TRUNCATED AT 400 WORDS)

Electrophysiology of the mammillary complex in vitro. I. Tuberomammillary and lateral mammillary neurons

1992 ◽  
Vol 68 (4) ◽  
pp. 1307-1320 ◽  
Author(s):  
R. R. Llinas ◽  
A. Alonso
Keyword(s):  
Membrane Potential ◽  
Lucifer Yellow ◽  
Outward Current ◽  
Repetitive Firing ◽  
Inward Rectification ◽  
Resting Membrane Potential ◽  
Transient Outward Current ◽  
Mammillary Body ◽  
Pacemaker Current

1. The electrophysiological properties of the tuberomammillary and lateral mammillary neurons in the guinea pig mammillary body were studied using an in vitro brain slice preparation. 2. Tuberomammillary (n = 79) neurons were recorded mainly ventral to the lateral mammillary body as well as ventromedially to the fornix within the rostral part of the medial mammillary nucleus. Intracellular staining with horseradish peroxidase (n = 9) and Lucifer yellow (n = 3) revealed that these cells have several thick, long, spiny dendrites emerging from large (20-35 microns) fusiform somata. 3. Most tuberomammillary neurons (66%) fired spontaneously at a relatively low frequency (0.5-10 Hz) at the resting membrane potential. The action potentials were broad (2.3 ms) with a prominent Ca(2+)-dependent shoulder on the falling phase. Deep (17.8 mV), long-lasting spike afterhyperpolarizations were largely Ca(2+)-independent. 4. All tuberomammillary neurons recorded displayed pronounced delayed firing when the cells were activated from a potential negative to the resting level. The cells also displayed a delayed return to the baseline at the break of hyperpolarizing pulses applied from a membrane potential level close to firing threshold. Analysis of the voltage- and time dependence of this delayed rectification suggested the presence of a transient outward current similar to the A current (IA). These were not completely blocked by high concentrations of 4-aminopyridine, whereas the delayed onset of firing was always abolished when voltage-dependent Ca2+ conductances were blocked by superfusion with Cd2+. 5. Tuberomammillary neurons also displayed inward rectification in the hyperpolarizing and, primarily, depolarizing range. Block of voltage-gated Na(+)-dependent conductances with tetrodotoxin (TTX) selectively abolished inward rectification in the depolarizing range, indicating the presence of a persistent low-threshold sodium-dependent conductance (gNap). In fact, persistent TTX-sensitive, plateau potentials were always elicited following Ca2+ block with Cd2+ when K+ currents were reduced by superfusion with tetraethylammonium. 6. The gNap in tuberomammillary neurons may subserve the pacemaker current underlying the spontaneous firing of these cells. The large-amplitude spike afterhyperpolarization of these neurons sets the availability of the transient outward rectifier, which, in conjunction with the pacemaker current, establishes the rate at which membrane potential approaches spike threshold. 7. Repetitive firing elicited by direct depolarization enhanced the spike shoulder of tuberomammillary neurons. Spike trains were followed by a Ca(2+)-dependent, apamine-sensitive, slow afterhyperpolarization. 8. Lateral mammillary neurons were morphologically and electrophysiologically different from tuberomammillary neurons. All lateral mammillary neurons neurons recorded (n = 44) were silent at rest (-60 mV).(ABSTRACT TRUNCATED AT 400 WORDS)

scholarly journals Autoactivity of A5 neurons: role of subthreshold oscillations and persistent Na+current

1997 ◽  
Vol 273 (5) ◽  
pp. H2280-H2289 ◽  
Author(s):  
Donghai Huangfu ◽  
Patrice G. Guyenet
Keyword(s):  
Membrane Potential ◽  
Discharge Rate ◽  
Input Resistance ◽  
Frequency Component ◽  
Inward Rectification ◽  
Intrinsic Properties ◽  
Potential Oscillations ◽  
Subthreshold Oscillations

A5 noradrenergic neurons play a key role in autonomic regulation, nociception, and respiration. The purpose of the present experiments was to characterize some of the intrinsic properties of A5 cells in vitro. Whole cell recordings were obtained from 85 spinally projecting neurons of the ventrolateral pons of neonate rats. Immunohistochemistry showed that 60% of the ventrolateral pontine cells were noradrenergic. Eighty percent of A5 neurons were spontaneously active (0.1–5.5 spikes/s). Their discharge rate was unchanged by a mixture of synaptic blockers that eliminated postsynaptic potentials (PSPs). The nonnoradrenergic cells could not be distinguished from A5 cells on the basis of discharge rate, action potential duration, inward rectification, input resistance, or accommodation. A5 cells displayed subthreshold irregular oscillations of the membrane potential (main frequency component 0.5–2 Hz). These oscillations were unchanged in the presence of low external Ca2+-high Mg2+ and were very reduced by hyperpolarizing the cells below −65 mV. The oscillations were partially attenuated by 1 μM tetrodotoxin (TTX) and were eliminated by reducing external Na+ (27 mM). Stepping the membrane potential from −65 to −50 mV for 200 ms revealed the presence of a transient and a persistent inward current that were both blocked by 0.1 μM TTX or by extracellular Na+ reduction. In conclusion, most A5 neurons are spontaneously active in vitro. They display irregular subthreshold membrane potential oscillations generated by voltage-activated conductances that include a persistent TTX-sensitive Na+ current. Most of the activity of A5 cells appears due to intrinsic properties rather than to synaptic inputs.

scholarly journals Ionic channels of the inner segment of tiger salamander cone photoreceptors.

1989 ◽  
Vol 94 (4) ◽  
pp. 719-743 ◽  
Author(s):  
S Barnes ◽  
B Hille
Keyword(s):  
Ionic Currents ◽  
Ionic Channels ◽  
High Threshold ◽  
Ca Channel ◽  
Cone Photoreceptors ◽  
Feedback Effects ◽  
Cation Current ◽  
Low Threshold ◽  
Small Voltage ◽  
K Currents

Cone photoreceptors were isolated enzymatically and their ionic currents studied by the whole-cell, gigaseal voltage-clamp technique. Five nonsynaptic currents were identified. A prominent, poorly selective cation current, Ih, activated after a delay during hyperpolarizations and then deactivated with a delay on return to potentials greater than -50 mV. An empirical model for Ih gating kinetics is developed with three open and two closed states. Depolarization elicits a small, voltage-gated calcium current (ICa). Block by nitrendipine, nickel, cadmium, and cobalt, increase of current with barium, lack of rapid inactivation, and relatively high threshold suggest an L-type Ca channel. No evidence was found for low-threshold Ca channels. An anion current ICl(Ca) was present after pulses that led to a significant inward ICa (but not IBa) and was not elicited when cobalt was present. Tails of ICl(Ca) were short (100 ms) after short depolarizations and were longer after longer depolarizations. Two TEA-sensitive K currents were also elicited by depolarizations. One, IK(Ca), was calcium sensitive. We looked for modulation of Ih, ICa, and ICl(Ca) by a number of neurotransmitters. No changes of Ih were seen, but ICa and ICl(Ca) were depressed in a few cones when GABA or adenosine were applied. We discuss how this modulation might contribute to the feedback effects of horizontal cells on cones when surrounding cones are illuminated.

Membrane properties of rat subicular neurons in vitro

1993 ◽  
Vol 70 (3) ◽  
pp. 1244-1248 ◽  
Author(s):  
D. Mattia ◽  
G. G. Hwa ◽  
M. Avoli
Keyword(s):  
Hippocampal Slices ◽  
Rhythmic Activity ◽  
Input Resistance ◽  
Membrane Properties ◽  
Inward Rectification ◽  
Resting Membrane Potential ◽  
Channel Blockers ◽  
Electrophysiological Properties ◽  
Low Threshold

1. Conventional intracellular recordings were performed in rat hippocampal slices to investigate the electrophysiological properties of subicular neurons. These cells had a resting membrane potential (RMP) of -66 +/- 7.2 mV (mean +/- SD; n = 50), input resistance of 23.6 +/- 8.2 M omega (n = 51), time constant of 7.1 +/- 1.9 ms (n = 51), action potential amplitude of 85.8 +/- 13.8 mV (n = 50), and duration of 2.9 +/- 1.2 ms (n = 48). Analysis of the current-voltage relationship revealed membrane inward rectification in both depolarizing and hyperpolarizing direction. The latter type was readily abolished by Cs+ (3 mM; n = 6 cells). 2. Injection of depolarizing current pulses of threshold intensity induced in all subicular neurons (n = 51) recorded at RMP a burst of two to three fast action potentials (frequency = 212.7 +/- 90 Hz, n = 13 cells). This burst rode on a slow depolarizing envelope and was followed by an afterhyperpolarization and later by regular spiking mode once the pulse was prolonged. Similar bursts were also generated upon termination of a hyperpolarizing current pulse. 3. The slow depolarization underlying the burst resembled a low-threshold response, which in thalamic cells is caused by a Ca2+ conductance and is contributed by the Cs(+)-sensitive inward rectifier. However, bursts in subicular cells persisted in medium containing the Ca(2+)-channel blockers Co2+ (2 mM) and Cd2+ (1 mM) (n = 5 cells) but disappeared during application of TTX (1 microM; n = 3 cells). Hence they were mediated by Na+. Blockade of the hyperpolarizing inward rectification by Cs+ did not prevent the rebound response (n = 3 cells). 4. Our findings demonstrate that intrinsic bursts, presumably related to a "low-threshold" Na+ conductance are present in rat subicular neurons. Similar intrinsic characteristics have been suggested to underlie the rhythmic activity described in other neuronal networks, although in most cases the low-threshold electrogenesis was caused by Ca2+. We propose that the bursting mechanism might play a role in modulating incoming signals from the classical hippocampal circuit within the limbic system.

scholarly journals Relationship of membrane properties, spike burst responses, laminar location, and functional class of dorsal horn neurons recorded in vitro

2016 ◽  
Vol 116 (3) ◽  
pp. 1137-1151 ◽  
Author(s):  
Patrick M. Dougherty ◽  
Jinghong Chen
Keyword(s):  
Dorsal Root ◽  
Dynamic Range ◽  
Functional Class ◽  
Membrane Properties ◽  
Resting Membrane Potential ◽  
High Threshold ◽  
Wide Dynamic Range ◽  
Low Threshold ◽  
Wide Dynamic Range Neurons

The input-output and discharge properties of neurons are shaped by both passive and active electrophysiological membrane properties. Whole cell patch-clamp recordings in lamina I–III neurons in an isolated preparation of the whole spinal cord of juvenile rats with attached dorsal roots and dorsal root ganglia were used to further define which of these properties provides the most impactful classification strategy. A total of 95 neurons were recorded in segment L5 and were classified based on the responses to L4 dorsal root stimulation. The results showed that high-threshold and silent neurons had higher membrane resistance and more negative resting membrane potential than low-threshold or wide-dynamic-range neurons. Rheobase in low-threshold and wide-dynamic-range neurons was significantly lower than that of high-threshold or silent neurons. Four types of firing patterns were identified in response to depolarizing current injections. Low-threshold cells most frequently showed a phasic firing pattern characterized by a short initial burst of action potentials, single spiking or irregular firing bursts at the onset of a depolarizing pulse. High-threshold and wide-dynamic-range neurons were characterized by tonic firing with trains of spikes occurring at regular intervals throughout the current pulse. The majority of silent neurons displayed a delayed onset of firing in response to current injection. These results indicate that the passive membrane properties of spinal neurons are tuned to optimize the responses to particular subsets of afferent stimuli.

Force dependent response reversal mediated by low- and high-threshold afferents from the same mechanoreceptor in a crayfish leg

1996 ◽  
Vol 76 (3) ◽  
pp. 1540-1544 ◽  
Author(s):  
C. S. Leibrock ◽  
A. R. Marchand ◽  
W. J. Barnes
Keyword(s):  
Mechanical Stimulation ◽  
Sense Organ ◽  
High Threshold ◽  
Intracellular Recordings ◽  
Defensive Responses ◽  
Response Reversal ◽  
Low Threshold ◽  
Excitatory Responses ◽  
Different Levels

1. The reflex responses initiated by cuticular stress detector one (CSD1) afferents in anterior levator motor neurnons in the fifth walking leg of crayfish were studied in an in vitro preparation by means of intracellular recordings. 2. The response in the anterior levator reversed with strong mechanical stimulation. Inhibitory responses were correlated with the activation of low-threshold CSD1 units, excitatory responses with the activation of high-threshold CSD1 units. Two opposing reflexes thus originate from the same sense organ at different levels of stimulation. 3. Some low-threshold units were inactive at stimulus strengths that activated the high-threshold units. Other low-threshold units remained active. Their reflex effects were reduced by either pre- or postsynaptic mechanisms. 4. Functionally, this force dependent response reversal could be important in switching from postural/locomotor responses to defensive responses such as limb autotomy.

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