Functional Significance of Passive and Active Dendritic Properties in the Synaptic Integration by an Identified Nonspiking Interneuron of Crayfish

2006 ◽  
Vol 96 (6) ◽  
pp. 3157-3169 ◽  
Author(s):  
Akira Takashima ◽  
Ryou Hikosaka ◽  
Masakazu Takahata
Keyword(s):  
Functional Significance ◽  
Attenuation Factor ◽  
Three Dimensional ◽  
Spatial Summation ◽  
Synaptic Integration ◽  
Resting Potential ◽  
Factor V ◽  
Synaptic Potential ◽  
Synaptic Potentials ◽  
Nonspiking Interneuron

Nonspiking interneurons control their synaptic output directly by membrane potential changes caused by synaptic activities. Although these interneurons do not generate spikes, their dendritic membrane is endowed with a variety of voltage-dependent conductances whose functional significance in synaptic integration remains unknown. We quantitatively investigated how the passive and active dendritic properties affect the synaptic integration in an identified nonspiking interneuron of crayfish by computer simulation using its multicompartment model based on electrophysiological measurements and three-dimensional morphometry. At the resting potential level, the attenuation factor ( Vs/ Vt) of a unitary synaptic potential in the course of its spread from a dendritic terminal ( Vs) to other terminals ( Vt) ranged from 4.42 to 6.30 with no substantial difference between hyperpolarizing and depolarizing potentials. The compound synaptic responses to strong mechanosensory stimulation could be reproduced in calculation only as the result of spatial summation of attenuated potentials, not as any single large potential. The characteristic response could be reproduced by assuming that the active conductances were distributed only in the dendritic region where the synaptic summation was carried out. The active conductances in other parts of the cell affected neither the shape of the compound synaptic response nor the dendritic spread of synaptic potentials. These findings suggest that the active membrane conductances do not affect the spatial distribution of synaptic potentials over dendrites but function in sculpting the summed synaptic potential to enhance temporal resolution in the synaptic output of the nonspiking interneuron.

GABA- and glutamate-mediated synaptic potentials in rat dorsal raphe neurons in vitro

1989 ◽  
Vol 61 (4) ◽  
pp. 719-726 ◽  
Author(s):  
Z. Z. Pan ◽  
J. T. Williams
Keyword(s):  
Amino Acid ◽  
Excitatory Amino Acid ◽  
Dorsal Raphe ◽  
Potassium Citrate ◽  
Resting Potential ◽  
Synaptic Potential ◽  
Synaptic Potentials ◽  
Dorsal Raphé ◽  
Raphe Neurons

1. Synaptic potentials were recorded with intracellular electrodes from rat dorsal raphe neurons in a slice preparation. 2. Synaptic potentials were evoked by applying electrical pulses to bipolar stimulating electrodes positioned immediately dorsal to the raphe nucleus; these arose after a latency of 0.5-5 ms and had a duration of 20-200 ms. 3. The synaptic potential was biphasic (at the resting potential) when the recording electrodes contained potassium citrate; a depolarization was followed by a hyperpolarization. The hyperpolarization reversed in polarity at -70 mV and was blocked by bicuculline. 4. The depolarizing synaptic potential was reduced to 50-90% of control by kynurenate (1-2 mM) or 6-cyano-2,3-dihydroxy-7-nitro-quinoxaline (CNQX) (10 microM) and increased in amplitude and duration by magnesium-free solution. 5. In magnesium-free solutions (with CNQX), the depolarizing synaptic potential was blocked by DL-2-amino-5-phosphonovaleric acid (APV, 50 microM). APV also blocked depolarization caused by adding N-methyl-D-aspartate (NMDA) to the superfusion solution. 6. The results indicate that raphe neurons display two synaptic potentials having a duration of 150-200 ms: one that is mediated by GABA and a second that is due to an excitatory amino acid. The component mediated by an excitatory amino acid involves, in part, a receptor of the NMDA type.

scholarly journals Analysis of structural similarities between brain Thy-1 antigen and immunoglobulin domains. Evidence for an evolutionary relationship and a hypothesis for its functional significance

1981 ◽  
Vol 195 (1) ◽  
pp. 31-40 ◽  
Author(s):  
F E Cohen ◽  
J Novotný ◽  
M J E Sternberg ◽  
D G Campbell ◽  
A F Williams
Keyword(s):  
Functional Significance ◽  
Structure Prediction ◽  
Secondary Structure Prediction ◽  
Three Dimensional ◽  
Evolutionary Relationship ◽  
Dimensional Structure ◽  
Sequence Homologies ◽  
Beta Structure ◽  
Beta 2 Microglobulin

The Thy-1 membrane glycoprotein from rat brain is shown to have structural and sequence homologies with immunoglobulin (Ig) domains on the basis of the following evidence. 1. The two disulphide bonds of Thy-1 are both consistent with the Ig-fold. 2. The molecule contains extensive beta-structure as shown by the c.d. spectrum. 3. Secondary structure prediction locates beta-strands along the sequence in a manner consistent with the Ig-fold. 4. On the basis of rules derived from known beta-sheet structures, a three-dimensional structure with the Ig-fold is predicted as favourable for Thy-1. 5. Sequences in the proposed beta-strands of Thy-1 and known beta-strands of Ig domains show significant sequence homology. This homology is statistically more significant than for the comparison of proposed beta-strand sequences of beta 2-microglobulin with Ig domains. An hypothesis is presented for the possible functional significance of an evolutionary relationship between Thy-1 and Ig. It is suggested that both Thy-1 and Ig evolved from primitive molecules, with an Ig fold, which mediated cell--cell interactions. The present-day role of Thy-1 may be similar to that of the primitive domain.

A Fast Synaptic Potential Mediated by NMDA and Non-NMDA Receptors

1997 ◽  
Vol 78 (5) ◽  
pp. 2693-2706 ◽  
Author(s):  
Laura R. Wolszon ◽  
Alberto E. Pereda ◽  
Donald S. Faber
Keyword(s):  
Nmda Receptor ◽  
Nmda Receptors ◽  
Resting Potential ◽  
Repetitive Firing ◽  
Physiological Data ◽  
Receptor Subtypes ◽  
Excitatory Postsynaptic Potential ◽  
Synaptic Potential ◽  
Synaptic Currents ◽  
Fast Kinetics

Wolszon, Laura R., Alberto E. Pereda, and Donald S. Faber. A fast synaptic potential mediated by NMDA and non-NMDA receptors. J. Neurophysiol. 78: 2693–2706, 1997. Excitatory synaptic transmission in the CNS often is mediated by two kinetically distinct glutamate receptor subtypes that frequently are colocalized, the N-methyl-d-aspartate (NMDA) and non-NMDA receptors. Their synaptic currents are typically very slow and very fast, respectively. We examined the pharmacological and physiological properties of chemical excitatory transmission at the mixed electrical and chemical synapses between auditory afferents and the goldfish Mauthner cell, in vivo. Previous physiological data have suggested the involvement of glutamate receptors in this fast excitatory postsynaptic potential (EPSP), the chemical component of which decays with a time constant of <2 ms. We demonstrate here that the pharmacological and voltage-dependent characteristics of the synaptic currents are consistent with glutamatergic transmission and that both NMDA and non-NMDA receptors are involved. The two components surprisingly exhibit quite similar kinetics even at resting potential, with the NMDA response being only slightly slower. Due to its fast kinetics and characteristic voltage dependence, NMDA receptor-mediated transmission at these first-order synapses contributes significantly to paired pulse and frequency-dependent facilitation of successive fast EPSPs during high-frequency repetitive firing, a presynaptic impulse pattern that induces activity-dependent homosynaptic changes in both electrical and chemical transmission. Thus NMDA receptor kinetics in this intact preparation are suited to its functional requirements, namely speed of information transmission and the ability to trigger changes in synaptic efficacy.

scholarly journals Spatial model of the gecko foot hair: functional significance of highly specialized non-uniform geometry

2015 ◽  
Vol 5 (1) ◽  
pp. 20140065 ◽  
Author(s):  
Alexander E. Filippov ◽  
Stanislav N. Gorb
Keyword(s):  
Functional Significance ◽  
Spatial Model ◽  
Rough Surfaces ◽  
Three Dimensional ◽  
Intermolecular Forces ◽  
Dimensional Structure ◽  
Fractal Surface ◽  
Flexible Form ◽  
Spatial Geometry ◽  
Adhesive Contacts

One of the important problems appearing in experimental realizations of artificial adhesives inspired by gecko foot hair is so-called clusterization. If an artificially produced structure is flexible enough to allow efficient contact with natural rough surfaces, after a few attachment–detachment cycles, the fibres of the structure tend to adhere one to another and form clusters. Normally, such clusters are much larger than original fibres and, because they are less flexible, form much worse adhesive contacts especially with the rough surfaces. Main problem here is that the forces responsible for the clusterization are the same intermolecular forces which attract fibres to fractal surface of the substrate. However, arrays of real gecko setae are much less susceptible to this problem. One of the possible reasons for this is that ends of the seta have more sophisticated non-uniformly distributed three-dimensional structure than that of existing artificial systems. In this paper, we simulated three-dimensional spatial geometry of non-uniformly distributed branches of nanofibres of the setal tip numerically, studied its attachment–detachment dynamics and discussed its advantages versus uniformly distributed geometry.

Subthreshold oscillations of the membrane potential: a functional synchronizing and timing device

1993 ◽  
Vol 70 (5) ◽  
pp. 2181-2186 ◽  
Author(s):  
I. Lampl ◽  
Y. Yarom
Keyword(s):  
Membrane Potential ◽  
Logic Gate ◽  
Maximum Amplitude ◽  
Sine Wave ◽  
Inferior Olivary Nucleus ◽  
Synaptic Potential ◽  
Synaptic Potentials ◽  
Subthreshold Oscillations ◽  
Inferior Olivary ◽  
Olivary Nucleus

1. Subthreshold membrane potential oscillations have been observed in different types of CNS neurons. In this in vitro study, we examined the possible role of these oscillations by analyzing the responses of neurons from the inferior olivary nucleus to a combined stimulation of sine wave and synaptic potentials. 2. A nonlinear summation of the sine wave and the synaptic potential occurred in olivary neurons; a superlinear summation occurred when the synaptic potential was elicited at the trough of the sine wave or during the rising phase. On the other hand, a less than linear summation occurred when the synaptic potentials were evoked during the falling phase of the wave. 3. Significant changes in the delay of the synaptic responses were observed. As a result of these changes, the maximum amplitude of the response occurred at the peak of the sine wave, regardless of the exact time of stimulation. The output of the neuron was therefore synchronized with the sine wave and depended only partly on the input phase. 4. These data demonstrate that neurons from the inferior olivary nucleus are capable of operating as accurate synchronizing devices. Moreover, by affecting the delay line, they act as a logic gate that ensures that the information will be added to the system only at given times.

Sustained depolarizing potentials in reticulospinal axons during evoked seizure activity in lamprey spinal cord

1978 ◽  
Vol 41 (2) ◽  
pp. 384-393 ◽  
Author(s):  
G. Matthews ◽  
W. O. Wickelgren
Keyword(s):  
Spinal Cord ◽  
Membrane Potential ◽  
Input Resistance ◽  
Response Amplitude ◽  
Resting Potential ◽  
Mammalian Brain ◽  
Extracellular Potassium ◽  
Synaptic Potential ◽  
Axonal Membrane ◽  
Passive Current

1. Intracellular recordings were made from lamprey reticulospinal axons (Muller axons) during seizures evoked by electrical stimulation of the isolated spinal cord in saline containing either 0 Cl or 1 mM picrotoxin. The seizures had tonic and clonic-phases similar to ictal seizures in mammalian brain. 2. During seizures Muller axons were depolarized by 10-15 mV. These seizure-depolarizations were not due to any direct effect of the evoking stimulus on the Muller axons themselves nor were they initiated by an accumulation or extracellular potassium. 3. A decrease in axonal input resistance occurred during a seizure-depolarization. Also, the amplitude of a seizure-depolarization was decreased by depolarizing the axon 5-15 mV with injected current. Further, hyperpolarizing the axon increased the amplitude of the seizure-depolarization, but the growth flattened out beyond 30-40 mV of hyperpolarization. The decrease in input resistance during the seizure-depolarization and the dependence of the response amplitude on axonal membrane potential suggested that the seizure-depolarization was an excitatory synaptic potential. However, the failure of the seizure-depolarization amplitude to continue to grow at membrane potentials greater than 30 mV negative to the resting potential was not consistent with this interpretation. 4. A synaptic conductance change as the cause of the seizure-depolarization was ruled out by setting the axonal membrane potential at different levels with injected current and monitoring the input resistance of the axon before and during seizure-depolarizations. It was found that no change in input resistance occurred during the seizure-depolarization when the axon was hyperpolarized more than approximately 30 mV, the same potential at which the growth in the response amplitude ceased. From analysis of these data and the passive current-voltage properties of Muller axons it is concluded that the seizure-depolarization is not a chemical synaptic potential, but rather the result of the passive injection of depolarizing current into the axons. 5. The source of the depolarizing current which flows into Muller axons during seizures is probably paroxysmal action-potential activity in spinal motoneurons and interneurons, many of which are electrically coupled to Muller axons.

Cholinergic suppression specific to intrinsic not afferent fiber synapses in rat piriform (olfactory) cortex

1992 ◽  
Vol 67 (5) ◽  
pp. 1222-1229 ◽  
Author(s):  
M. E. Hasselmo ◽  
J. M. Bower
Keyword(s):  
Piriform Cortex ◽  
Afferent Fiber ◽  
Extracellular Recording ◽  
Synaptic Potential ◽  
Response Curves ◽  
Cholinergic Agonists ◽  
Synaptic Potentials ◽  
Cholinergic Agonists And Antagonists ◽  
Synaptic Responses

1. Differences in the cholinergic suppression of afferent and intrinsic fiber synaptic transmission were studied in the rat piriform cortex. Extracellular and intracellular recording techniques were applied in an in vitro transverse slice preparation. Afferent and intrinsic fiber systems were differentially stimulated with electrodes placed in layer Ia or layer Ib, respectively. Synaptic responses were monitored in the presence of cholinergic agonists and antagonists. 2. Afferent and intrinsic fiber synaptic potentials measured extracellularly showed large differences in sensitivity to micromolar concentrations of the cholinergic agonists carbachol or (+/-)-muscarine, or to acetylcholine combined with neostigmine. Intrinsic fiber synaptic responses in layer Ib were strongly reduced in the presence of cholinergic agonists, whereas afferent fiber synaptic responses in layer Ia were largely unaffected. At a concentration of 100 microM, all three agonists caused a greater than 60% decrease in the height of the intrinsic fiber synaptic potential but less than 15% reduction in the afferent fiber synaptic potential. 3. Intracellular recordings confirmed that the cholinergic agonist carbachol selectively suppresses intrinsic fiber synaptic potentials but not afferent fiber synaptic potentials recorded from the same pyramidal cell. 4. Dose-response curves to carbachol were obtained for both fiber systems using extracellular recording of evoked field potentials. Carbachol suppressed intrinsic fiber synaptic potentials with a coefficient of dissociation (KD) estimated at 2.9 microM and an inhibitory concentration for 50% response estimated at 6.6 microM. 5. Carbachol produced a proportionately greater suppression of the first pulse than the second pulse of a pulse pair. This increase in the level of facilitation accompanying suppression suggests a presynaptic mechanism.(ABSTRACT TRUNCATED AT 250 WORDS)

Distribution of rubrospinal synaptic input to cat triceps surae motoneurons

1993 ◽  
Vol 70 (4) ◽  
pp. 1460-1468 ◽  
Author(s):  
R. K. Powers ◽  
F. R. Robinson ◽  
M. A. Konodi ◽  
M. D. Binder
Keyword(s):  
Discharge Rate ◽  
Red Nucleus ◽  
Triceps Surae ◽  
Resting Potential ◽  
Repetitive Firing ◽  
Projection Area ◽  
Mean Values ◽  
Synaptic Potentials ◽  
Wide Range ◽  
Repetitive Discharge

1. We evoked steady-state synaptic potentials in triceps surae motoneurons of the cat by stimulating the hindlimb projection area of the contralateral magnocellular red nucleus at 200 Hz. We measured the effective synaptic currents (IN) underlying the synaptic potentials using a modified voltage-clamp technique. We also determined the effect of the rubrospinal input on the discharge rate of some of the motoneurons by inducing repetitive discharge with long injected current pulses during which the red nucleus stimulation was repeated. 2. At motoneuron resting potential, the distribution of IN from the red nucleus within the triceps surae pools was qualitatively similar to the distribution of synaptic potentials: 86% of the putative type F motoneurons received a net depolarizing IN from the red nucleus stimulation, whereas only 38% of the putative type S units did so. The mean values of IN were significantly different in the two groups [+4.1 +/- 5.0 nA (SD) for putative type F and -1.6 +/- 3.1 nA for putative type S]. 3. However, when the values of IN at threshold for repetitive firing were estimated, the distribution of IN from the red nucleus was quite different. At threshold, all of the putative type S units received hyperpolarizing IN but so did nearly half of the putative type F units. 4. As would be expected from the wide range of IN at threshold (-20 to +12 nA), the red nucleus input produced dramatically different effects on the discharge of different motoneurons.(ABSTRACT TRUNCATED AT 250 WORDS)

scholarly journals Integrative Synaptic Mechanisms in the Caudal Ganglion of the Crayfish

1960 ◽  
Vol 43 (3) ◽  
pp. 671-681 ◽  
Author(s):  
James B. Preston ◽  
Donald Kennedy
Keyword(s):  
Single Pulse ◽  
Afferent Input ◽  
Abdominal Ganglion ◽  
Synaptic Potential ◽  
Fiber Membrane ◽  
Spike Generation ◽  
Spike Discharge ◽  
Synaptic Potentials ◽  
Synaptic Mechanisms ◽  
Pulse Stimulation

A study of activity recorded with intracellular micropipettes was undertaken in the caudal abdominal ganglion of the crayfish in order to gain information about central fiber to fiber synaptic mechanisms. This synaptic system has well developed integrative properties. Excitatory post-synaptic potentials can be graded, and synaptic potentials from different inputs can sum to initiate spike discharge. In most impaled units, the spike discharge fails to destroy the synaptic potential, thereby allowing sustained depolarization and multiple spike discharge following single pulse stimulation to an afferent input. Some units had characteristics which suggest a graded threshold for spike generation along the post-synaptic fiber membrane. Other impaled units responded to afferent stimulation with spike discharges of two distinct amplitudes. The smaller or "abortive" spikes in such units may represent non-invading activity in branches of the post-synaptic axon. On a few occasions one afferent input was shown to inhibit the spike discharge initiated by another presynaptic input.

scholarly journals V-Factor Indicator in the Assessment of the Change in the Attractiveness of View as a Result of the Implementation of a Specific Planning Scenario

2019 ◽  
Vol 8 (2) ◽  
pp. 78
Author(s):  
Magda Pluta ◽  
Bartosz Mitka
Keyword(s):  
Factor Analysis ◽  
Dimensional Space ◽  
Three Dimensional ◽  
Observation Point ◽  
View Factor ◽  
Factor V ◽  
Average Value ◽  
3D Space ◽  
The Aesthetic ◽  
Special Points

This paper describes the algorithm of the view factor (V-factor). It is based on an analysis of visibility, taking into account the attractiveness of the observed elements in a three-dimensional space. The results of the V-factor analysis provide input for the decision-making process when selecting the most advantageous planning scenario so that the harmony of landscape and ecological balance can be maintained. The V-factor indicator can be successfully used in the process of spatial planning, in particular, at the stage of determining the parameters of new buildings and lines of sight between planned buildings. The purpose of the indicator is to determine the numerical values for observation points, thus facilitating a comparative assessment of the attractiveness of view available from the special points in space. The analysis uses a 3D space model that includes an integrated existing and planning state designed on the basis of planning scenarios. The V-factor analysis takes into account the distance of the observation point from the observed object, vertical and horizontal angles of observation, and the aesthetic value of the observed object. As a result, an average value of the V-factor indicator was obtained for each planning scenario, which facilitated the determination of the more beneficial one in terms of the attractiveness of view.

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