Posttetanic potentiation of group Ia EPSPs: possible mechanisms for differential distribution among medial gastrocnemius motoneurons

1983 ◽  
Vol 50 (2) ◽  
pp. 379-398 ◽  
Author(s):  
A. Lev-Tov ◽  
M. J. Pinter ◽  
R. E. Burke
Keyword(s):  
Negative Correlation ◽  
Action Potentials ◽  
Input Resistance ◽  
Mean Amplitude ◽  
Synaptic Depression ◽  
Medial Gastrocnemius ◽  
Posttetanic Potentiation ◽  
Differential Distribution ◽  
Strong Negative Correlation ◽  
Statistical Probability

We have reinvestigated the phenomenon of posttetanic potentiation (PTP) of group Ia monosynaptic excitatory postsynaptic potentials (EPSPs) in medial gastrocnemius (MG) alpha-motoneurons of pentobarbital-anesthetized cats. The results generally confirm earlier reports by Luscher and colleagues (43, 44) of a negative correlation between the maximum percentage potentiation of Ia EPSP amplitude (Pmax) and 1) the mean amplitude of the pretetanic control EPSP in the same cell and 2) the input resistance of the postsynaptic motoneuron. These negative correlations, which we will refer to as "differential distribution of PTP" within the MG motor pool, were less strong in the present work than reported by Luscher et al. (43, 44). We also found a relatively strong negative correlation between posttetanic EPSP depression, assessed by the amplitude of the first posttetanic EPSP, and the level of Pmax subsequently attained. We found no evidence that posttetanic depression is caused by failure of presynaptic action potentials. We investigated a second type of depression, referred to as "specific" synaptic depression, in which the second EPSP of paired responses (interval 250 ms) is, on average, smaller in peak amplitude than the first EPSP. This phenomenon appears to reflect decreases in the probability of transmitter release from previously activated synapses. Specific synaptic depression was consistently increased when paired responses were conditioned by a high-frequency tetanus. This is most easily explained by postulating that PTP results, at least in part, from an increase in the statistical probability of transmitter liberation from group Ia synapses that are activated (i.e., presumably invaded by action potentials) both before and after afferent tetanization. On the basis of the present results and other available evidence, we conclude that the differential distribution of PTP can be explained by two main factors: 1) the nonlinear relation between conductance and voltage changes inherent in all chemical synapses and 2) systematic variations in the properties of group Ia synapses that innervated different motoneurons, which remain to be clarified.

Calcium-dependent potassium conductance in rat supraoptic nucleus neurosecretory neurons

1985 ◽  
Vol 54 (6) ◽  
pp. 1375-1382 ◽  
Author(s):  
C. W. Bourque ◽  
J. C. Randle ◽  
L. P. Renaud
Keyword(s):  
Time Constant ◽  
Action Potentials ◽  
Supraoptic Nucleus ◽  
Potassium Conductance ◽  
Reversal Potential ◽  
Input Resistance ◽  
Mean Amplitude ◽  
Progressive Increase ◽  
Calcium Dependent ◽  
Neurosecretory Neurons

Intracellular recordings of rat supraoptic nucleus neurons were obtained from perfused hypothalamic explants. Individual action potentials were followed by hyperpolarizing afterpotentials (HAPs) having a mean amplitude of -7.4 +/- 0.8 mV (SD). The decay of the HAP was approximated by a single exponential function having a mean time constant of 17.5 +/- 6.1 ms. This considerably exceeded the cell time constant of the same neurons (9.5 +/- 0.8 ms), thus indicating that the ionic conductance underlying the HAP persisted briefly after each spike. The HAP had a reversal potential of -85 mV and was unaffected by intracellular Cl- ionophoresis of during exposure to elevated extracellular concentrations of Mg2+. In contrast, the peak amplitude of the HAP was proportional to the extracellular Ca2+ concentration and could be reversibly eliminated by replacing Ca2+ with Co2+, Mn2+, or EGTA in the perfusion fluid. During depolarizing current pulses, evoked action potential trains demonstrated a progressive increase in interspike intervals associated with a potentiation of successive HAPs. This spike frequency adaptation was reversibly abolished by replacing Ca2+ with Co2+, Mn2+, or EGTA. Bursts of action potentials were followed by a more prolonged afterhyperpolarization (AHP) whose magnitude was proportional to the number of impulses elicited (greater than 20 Hz) during a burst. Current injection revealed that the AHP was associated with a 20-60% decrease in input resistance and showed little voltage dependence in the range of -70 to -120 mV. The reversal potential of the AHP shifted with the extracellular concentration of K+ [( K+]o) with a mean slope of -50 mV/log[K+]o.(ABSTRACT TRUNCATED AT 250 WORDS)

Factors that control amplitude of EPSPs in dendritic neurons

1983 ◽  
Vol 50 (2) ◽  
pp. 399-412 ◽  
Author(s):  
A. Lev-Tov ◽  
J. P. Miller ◽  
R. E. Burke ◽  
W. Rall
Keyword(s):  
Synaptic Input ◽  
Preceding Paper ◽  
Input Resistance ◽  
Neuronal Membrane ◽  
Posttetanic Potentiation ◽  
Differential Distribution ◽  
Synaptic Density ◽  
Membrane Area ◽  
Membrane Resistivity ◽  
Specific Membrane

We have used a computer-based mathematical model of alpha-motoneurons and of group Ia synaptic input to them, based on anatomical and electrophysiological data from the cat spinal cord, in order to examine the effects of variations in neuron size and input resistance and of conductance magnitude and duration on the generation of excitatory postsynaptic potentials (EPSPs). The first set of calculations were designed to test the possible role of nonlinear EPSP summation in producing a differential distribution of posttetanic potentiation of group Ia EPSPs, described in the preceding paper (25; see also Refs. 26, 27). The results suggest that the negative correlations observed between the degree of posttetanic potentiation of Ia EPSPs and initial (pretetanic) EPSP amplitude as well as with the input resistance of the postsynaptic motoneurons can be explained in part by the inherent non-linearity between conductance change and the resultant potential change at chemical synapses. In a second set of calculations, we used the same model system to evaluate the effects produced by variations in neuronal membrane area, input resistance, and specific membrane resistivity, as well as of the density of excitatory synaptic input on the peak amplitude of EPSPs. With parameters constrained to match the properties of alpha-motoneurons and group Ia synaptic input, EPSP amplitudes were most sensitive to changes in synaptic density and were much less sensitive to alterations in neuron input resistance and specific membrane resistivity when synaptic density was constant.

Distribution of effective synaptic currents underlying recurrent inhibition in cat triceps surae motoneurons

1991 ◽  
Vol 65 (2) ◽  
pp. 168-177 ◽  
Author(s):  
A. D. Lindsay ◽  
M. D. Binder
Keyword(s):  
Steady State ◽  
Input Resistance ◽  
Recurrent Inhibition ◽  
Triceps Surae ◽  
Medial Gastrocnemius ◽  
High Threshold ◽  
Renshaw Cells ◽  
Differential Distribution ◽  
Synaptic Currents ◽  
Small Magnitude

1. Steady-state recurrent (Renshaw) inhibitory postsynaptic potentials (RIPSPs) were evoked in cat triceps surae motoneurons by stimulating the heteronymous muscle nerve at 100 Hz after dorsal root section. The effective synaptic currents (i.e., the net synaptic current measured at the soma, IN) underlying these inhibitory potentials were measured with a modified voltage-clamp technique. 2. The average value of the effective synaptic currents measured in medial gastrocnemius (MG) motoneurons was 0.4 nA. There was no significant correlation between the IN measured in individual cells and motoneuron input resistance (RN), rheobase (IR), duration of the spike afterhyperpolarization (AHPt1/2), or putative motor-unit type, although the steady-state inhibitory post-synaptic potential (IPSP) amplitudes were correlated with all of these parameters. 3. Steady-state recurrent inhibition was accompanied by a small (3.5%, on average) decrease in the resting input resistance of the motoneurons. The small magnitude of this measured change supports the hypothesis of Burke et al. that the site of synaptic contact between Renshaw cells and motoneurons is somewhat distal to the cell soma. 4. The absence of a differential distribution of the effective synaptic currents generated by Renshaw cells within the MG pool does not support the idea that recurrent inhibition mediates a selective reduction of the firing of small, low-threshold motoneurons by large, high-threshold motoneurons. The small amplitude of the effective synaptic currents we measured suggests that the contribution of recurrent inhibition to the direct modulation of motoneuron firing rate is subtle and that it is perhaps principally involved in the fine control and smooth production of muscle force.

Psoriasis and metabolic syndrome: comorbidity mechanisms

2019 ◽  
Vol 1 (7) ◽  
pp. 34-38
Author(s):  
E. V. Dontsova ◽  
O. Yu. Olisova ◽  
L. S. Kruglova
Keyword(s):  
Metabolic Syndrome ◽  
Negative Correlation ◽  
Inflammatory Cytokine ◽  
Antioxidant Ability ◽  
Weak Correlation ◽  
Strong Negative Correlation ◽  
The Metabolic Syndrome ◽  
Diagnostic Signs ◽  
Weak Negative Correlation ◽  
Correlation Link

Objectives: to study communications of separate components of the metabolic syndrome (MS) and immune and oxidative characteristics of patients with psoriasis in combination with MS. Methods. The research included 312 patients with psoriasis having diagnostic signs of a metabolic syndrome. Biochemical and immunological researches were conducted by means of immunofermental and immunokhemilyuminestsentny analyses. Results. At patients with psoriasis at a combination to MS abdominal obesity, a giperleptinemiya, insulin resistance, high oxidizing potential and hyperactivity of interleukins (ILS) -1β,-6,-8, a factor of a necrosis of tumors an alpha (FNO-α), interferon scale (INF-γ) are noted. the waist circle’ is characteristic direct weak correlation with the pro-inflammatory tsitokina oxidized by lipoproteins of blood (LDL-ok) and with the general oxidizing ability of blood (OOS), weak negative correlation of an indicator - with the general antioxidant ability of blood (OAS) and superoxide dismutase (SOD). The HOMA-IR index has direct correlation link of moderate force with levels of a leptin of blood, LDL-ok, OOS, pro-inflammatory tsitokin, negative correlation of moderate force - with OAS, SOD. At patients with psoriasis with MS direct strong correlation link of level of a leptin of blood with activity of the studied pro-inflammatory cytokine, LDL-ok, OOS moderated is established with the level of insulin in the blood., the HOMA-IR index, strong negative correlation with OAS, SOD. Conclusion. Presence at patients with psoriasis of signs of a metabolic syndrome is followed by increase in activity of immune and inflammatory mechanisms, development of oxidative stress.

Properties of visceral primary afferent neurons in the nodose ganglion of the rabbit

1985 ◽  
Vol 54 (2) ◽  
pp. 245-260 ◽  
Author(s):  
C. E. Stansfeld ◽  
D. I. Wallis
Keyword(s):  
Action Potentials ◽  
Input Resistance ◽  
Nodose Ganglion ◽  
Time Dependent ◽  
Membrane Properties ◽  
Resting Potential ◽  
Inward Rectification ◽  
C Cells ◽  
Axonal Conduction ◽  
A Cells

The active and passive membrane properties of rabbit nodose ganglion cells and their responsiveness to depolarizing agents have been examined in vitro. Neurons with an axonal conduction velocity of less than 3 m/s were classified as C-cells and the remainder as A-cells. Mean axonal conduction velocities of A- and C-cells were 16.4 m/s and 0.99 m/s, respectively. A-cells had action potentials of brief duration (1.16 ms), high rate of rise (385 V/s), an overshoot of 23 mV, and relatively high spike following frequency (SFF). C-cells typically had action potentials with a "humped" configuration (duration 2.51 ms), lower rate of rise (255 V/s), an overshoot of 28.6 mV, an after potential of longer duration than A-cells, and relatively low SFF. Eight of 15 A-cells whose axons conducted at less than 10 m/s had action potentials of longer duration with a humped configuration; these were termed Ah-cells. They formed about 10% of cells whose axons conducted above 2.5 m/s. The soma action potential of A-cells was blocked by tetrodotoxin (TTX), but that of 6/11 C-cells was unaffected by TTX. Typically, A-cells showed strong delayed (outward) rectification on passage of depolarizing current through the soma membrane and time-dependent (inward) rectification on inward current passage. Input resistance was thus highly sensitive to membrane potential close to rest. In C-cells, delayed rectification was not marked, and slight time-dependent rectification occurred in only 3 of 25 cells; I/V curves were normally linear over the range: resting potential to 40 mV more negative. Data on Ah-cells were incomplete, but in our sample of eight cells time-dependent rectification was absent or mild. C-cells had a higher input resistance and a higher neuronal capacitance than A-cells. In a proportion of A-cells, RN was low at resting potential (5 M omega) but increased as the membrane was hyperpolarized by a few millivolts. A-cells were depolarized by GABA but were normally unaffected by 5-HT or DMPP. C-cells were depolarized by GABA in a similar manner to A-cells but also responded strongly to 5-HT; 53/66 gave a depolarizing response, and 3/66, a hyperpolarizing response. Of C-cells, 75% gave a depolarizing response to DMPP.(ABSTRACT TRUNCATED AT 400 WORDS)

Growth and Development of the Wheat Tiller. II. The Dynamics of Tiller Growth

1975 ◽  
Vol 23 (5) ◽  
pp. 745 ◽  
Author(s):  
RF Williams ◽  
RHM Langer
Keyword(s):  
Negative Correlation ◽  
Growth And Development ◽  
Critical Event ◽  
Vascular Differentiation ◽  
Strong Negative Correlation ◽  
Physical Constraints ◽  
Size Dependent ◽  
Bud Growth ◽  
Time Relation ◽  
Tiller Bud

From an analysis of the length-time relation for tiller growth in wheat it was concluded that tillers which emerged traced a discontinuous curve, and that the discontinuity marked a critical event in tiller growth. Tiller buds which did not emerge as tillers continued to grow even more slowly, at least until anthesis of the primary shoot. The critical event was identified as that of escape from the cavity in which the bud was tightly contained throughout early development. The timing of vascular differentiation in tiller buds was shown to be size-dependent and there was no evidence for any correlation with the critical event of escape. A strong negative correlation between the lengths of the 3rd tiller buds and their subtending internodes was established, and the presence or absence of the 4th tiller bud was also correlated with its internode length. Current hypotheses relating to apical dominance are reviewed, and it is suggested that the dynamic physical constraints implicit in tiller bud growth add a further complication. It was concluded that hormonal, nutritional and constraint mechanisms need to be integrated as partial mechanisms which interacted at the interfaces between successive levels within apical systems.

scholarly journals Spatial Variation of the Relationship between PM2.5Concentrations and Meteorological Parameters in China

2015 ◽  
Vol 2015 ◽  
pp. 1-15 ◽  
Author(s):  
Gang Lin ◽  
Jingying Fu ◽  
Dong Jiang ◽  
Jianhua Wang ◽  
Qiao Wang ◽  
...  
Keyword(s):  
Negative Correlation ◽  
Meteorological Parameters ◽  
Semiarid Region ◽  
Strong Positive Correlation ◽  
Annual Average ◽  
Strong Negative Correlation ◽  
Positive Correlation ◽  
Humid Region ◽  
The Relationship ◽  
Warm Temperate

Epidemiological studies around the world have reported that fine particulate matter (PM2.5) is closely associated with human health. The distribution of PM2.5concentrations is influenced by multiple geographic and socioeconomic factors. Using a remote-sensing-derived PM2.5dataset, this paper explores the relationship between PM2.5concentrations and meteorological parameters and their spatial variance in China for the period 2001–2010. The spatial variations of the relationships between the annual average PM2.5, the annual average precipitation (AAP), and the annual average temperature (AAT) were evaluated using the Geographically Weighted Regression (GWR) model. The results indicated that PM2.5had a strong and stable correlation with meteorological parameters. In particular, PM2.5had a negative correlation with precipitation and a positive correlation with temperature. In addition, the relationship between the variables changed over space, and the strong negative correlation between PM2.5and the AAP mainly appeared in the warm temperate semihumid region and northern subtropical humid region in 2001 and 2010, with some localized differences. The strong positive correlation between the PM2.5and the AAT mainly occurred in the mid-temperate semiarid region, the humid, semihumid, and semiarid warm temperate regions, and the northern subtropical humid region in 2001 and 2010.

Motor-unit properties following cross-reinnervation of cat lateral gastrocnemius and soleus muscles with medial gastrocnemius nerve. II. Influence of muscle on motoneurons

1987 ◽  
Vol 57 (4) ◽  
pp. 1227-1245 ◽  
Author(s):  
R. C. Foehring ◽  
G. W. Sypert ◽  
J. B. Munson
Keyword(s):  
Electrical Properties ◽  
Motor Unit ◽  
Conduction Velocity ◽  
Decay Time ◽  
Motor Units ◽  
Input Resistance ◽  
Medial Gastrocnemius ◽  
Lateral Gastrocnemius ◽  
Mean Values ◽  
Axonal Conduction

We tested whether the muscle innervated may influence the expression of motoneuron electrical properties. Properties of individual motor units were examined following cross-reinnervation (X-reinnervation) of cat lateral gastrocnemius (LG) and soleus muscles by the medial gastrocnemius (MG) nerve. We examined animals at two postoperative times: 9-10 wk (medX) and 9-11 mo (longX). For comparison, normal LG and soleus motoneuron properties were also studied. Motor units were classified on the basis of their contractile responses as fast contracting fatigable, fast intermediate fast contracting fatigue resistant, and slow types FF, FI, FR, or S, respectively) (9, 21). Motoneuron electrical properties (rheobase, input resistance, axonal conduction velocity, afterhyperpolarization) were measured. After 9-11 mo, MG motoneurons that innervated LG muscle showed recovery of electrical properties similar to self-regenerated MG motoneurons. The relationships between motoneuron electrical properties were largely similar to self-regenerated MG. For MG motoneurons that innervated LG, motoneuron type (65) predicted motor-unit type in 74% of cases. LongX-soleus motoneurons differed from longX-LG motoneurons or self-regenerated MG motoneurons in mean values for motoneuron electrical properties. The differences in overall means reflected the predominance of type S motor units. The relationships between motoneuron electrical properties were also different than in self-regenerated MG motoneurons. In all cases, the alterations were in the direction of properties of type S units, and the relationship between normal soleus motoneurons and their muscle units. Within motor-unit types, the mean values were typical for that type in self-regenerated MG. Motoneuron type (65) was a fairly strong predictor of motor-unit type in longX soleus. MG motoneurons that innervated soleus displayed altered values for axonal conduction velocity, rheobase, and input resistance, which could indicate incomplete recovery from the axotomized state. However, although mean afterhyperpolarization (AHP) half-decay time was unaltered by axotomy (25), this parameter was significantly lengthened in MG motoneurons that innervated soleus muscle. There were, however, individual motoneuron-muscle-unit mismatches, which suggested that longer mean AHP half-decay time may also be due to incomplete recovery of a subpopulation of motoneurons. Those MG motoneurons able to specify soleus muscle-fiber type exhibited motoneuron electrical properties typical of that same motoneuron type in self-regenerated MG.(ABSTRACT TRUNCATED AT 400 WORDS)

Membrane resistance increases when automaticity develops in explanted rat heart cells

1990 ◽  
Vol 258 (1) ◽  
pp. H145-H152 ◽  
Author(s):  
O. F. Schanne ◽  
M. Lefloch ◽  
B. Fermini ◽  
E. Ruiz-Petrich
Keyword(s):  
Spontaneous Activity ◽  
Action Potentials ◽  
Ventricular Myocytes ◽  
Input Resistance ◽  
Membrane Resistance ◽  
Resting Potential ◽  
Heart Cells ◽  
Membrane Capacity ◽  
Rat Heart Cells ◽  
Specific Membrane

We compared the passive electrical properties of isolated ventricular myocytes (resting potential -65 mV, fast action potentials, and no spontaneous activity) with those of 2- to 7-day-old cultured ventricle cells from neonatal rats (resting potential -50 mV, slow action potentials, and presence of spontaneous activity). In myocytes the specific membrane capacity was 0.99 microF/cm2, and the specific membrane resistance increased from 2.46 k omega.cm2 at -65 mV to 7.30 k omega.cm2 at -30 mV. In clusters, the current-voltage relationships measured under current-clamp conditions showed anomalous rectification and the input resistance decreased from 1.05 to 0.48 M omega when external K+ concentration was increased from 6 to 100 mM. Using the model of a finite disk we determined the specific membrane resistance (12.9 k omega.cm2), the effective membrane capacity (17.8 microF/cm2), and the lumped resistivity of the disk interior (1,964 omega.cm). We conclude that 1) the voltage dependence of the specific membrane resistance cannot completely explain the membrane resistance increase that accompanies the appearance of spontaneous activity; 2) a decrease of the inwardly rectifying conductance (gk1) is mainly responsible for the increase in the specific membrane resistance and depolarization; and 3) approximately 41% of the inward-rectifying channels are electrically silent when spontaneous activity develops in explanted ventricle cells.

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