scholarly journals Synaptic action of Group I and II afferent fibres of muscle on the cells of the dorsal spinocerebellar tract

1961 ◽  
Vol 158 (3) ◽  
pp. 517-543 ◽  
Author(s):  
J. C. Eccles ◽  
O. Oscarsson ◽  
W. D. Willis
Keyword(s):  
Synaptic Action ◽  
Group I ◽  
Spinocerebellar Tract

Dorsal Spinocerebellar Tract Neurons Are Not Subjected to Postsynaptic Inhibition During Carbachol-Induced Motor Inhibition

1997 ◽  
Vol 78 (1) ◽  
pp. 137-144 ◽  
Author(s):  
Ming-Chu Xi ◽  
Jack Yamuy ◽  
Rong-Huan Liu ◽  
Francisco R. Morales ◽  
Michael H. Chase
Keyword(s):  
Spinal Cord ◽  
Membrane Potential ◽  
Synaptic Activity ◽  
Motor Inhibition ◽  
Postsynaptic Inhibition ◽  
Postsynaptic Potentials ◽  
Group I ◽  
The Mean ◽  
Spinocerebellar Tract ◽  
Clarke's Column

Xi, Ming-Chu, Jack Yamuy, Rong-Huan Liu, Francisco R. Morales, and Michael H. Chase. Dorsal spinocerebellar tract neurons are not subjected to postsynaptic inhibition during carbachol-induced motor inhibition. J. Neurophysiol. 78: 137–144, 1997. Dorsal spinocerebellar tract (DSCT) neurons in Clarke's column in the lumbar spinal cord of cats anesthetized with α-chloralose were recorded intracellularly. The membrane potential activity and electrophysiological properties of these neurons were examined before and during the state of active-sleep-like motor inhibition induced by the injection of carbachol into the nucleus pontis oralis. The synaptic activity of DSCT neurons during carbachol-induced motor inhibition did not change compared with that during control conditions. In particular, there was an absence of inhibitory postsynaptic potentials (IPSPs) in high-gain recordings from DSCT neurons and the resting membrane potential of DSCT neurons was not significantly hyperpolarized during carbachol-induced motor inhibition. The mean amplitude of both monosynaptic excitatory postsynaptic potentials and disynaptic IPSPs evoked in DSCT neurons following stimulation of group I muscle afferents after the injection of carbachol was similar to that evoked before the injection of carbachol. There were no significant changes in the mean input resistance and membrane time constant of DSCT neurons during carbachol-induced motor inhibition. We conclude that, in contrast to lumbar motoneurons, DSCT neurons in Clarke's column are not postsynaptically inhibited during carbachol-induced motor inhibition. Therefore the population of spinal cord Ib interneurons that inhibit both DSCT neurons and lumbar motoneurons is not likely to be the interneurons that are responsible for the postsynaptic inhibition of motoneurons that occurs during carbachol-induced motor inhibition. The present findings also indicate that transmission through the DSCT is not modulated by postsynaptic inhibition at the level of DSCT neurons during carbachol-induced motor inhibition.

Nonuniform release probabilities underlie quantal synaptic transmission at a mammalian excitatory central synapse

1988 ◽  
Vol 60 (3) ◽  
pp. 889-908 ◽  
Author(s):  
B. Walmsley ◽  
F. R. Edwards ◽  
D. J. Tracey
Keyword(s):  
Muscle Afferents ◽  
Single Fiber ◽  
Binomial Model ◽  
Release Probability ◽  
Group I ◽  
Unique Nature ◽  
Compound Binomial ◽  
Compound Binomial Model ◽  
Spinocerebellar Tract ◽  
Active Release

1. Excitatory postsynaptic potentials (EPSPs) evoked by impulses in single group I muscle afferents were recorded in dorsal spinocerebellar tract (DSCT) neurons in the spinal cords of anesthetized cats. Fluctuations in the amplitude of these single-fiber EPSPs were determined from measurements of EPSP peak amplitude and contaminating noise (800-4600 trials). 2. In a previous study at this connection, we found that these single-fiber EPSPs fluctuated in amplitude between approximately equal, or quantal, increments. However, these quantal fluctuations could not be described by simple binomial statistics (39). In the present study we have applied further analysis procedures to the same single-fiber EPSPs to formulate a more appropriate probabilistic model of transmission at this connection. 3. In the first stage we have demonstrated that each single-fiber EPSP is composed of the sum of a number (3-30) of uniform quantal events, and that there is extremely little variability in the amplitude of the single quantal event. 4. In a further procedure, we have demonstrated that these quantal fluctuations can be described by a compound binomial model in which each underlying quantal event is associated with a particular, but independent, release probability. The results of this analysis indicate that the probability of transmitter release varies considerably between release sites at this connection. (The use of such a compound binomial model reemphasized previous warnings concerning the interpretation of the results of all statistical models of quantal release. Problems regarding the non-unique nature of N, the total population of quantal events, and other such difficulties are discussed.) 5. A model of transmission at this connection is proposed, in which there are a number of "active" release sites, exhibiting generally high release probabilities, and a number of "reserve" release sites, with zero, or close to zero, release probability. The physiological consequences of such a scheme are discussed.

scholarly journals Collateral Actions of Premotor Interneurons on Ventral Spinocerebellar Tract Neurons in the Cat

2010 ◽  
Vol 104 (4) ◽  
pp. 1872-1883 ◽  
Author(s):  
E. Jankowska ◽  
P. Krutki ◽  
I. Hammar
Keyword(s):  
Muscle Spindles ◽  
Feedback Information ◽  
Inhibitory Postsynaptic Potentials ◽  
Group I ◽  
Muscle Nerve ◽  
Spinocerebellar Tract ◽  
Motor Nuclei ◽  
Group Ii ◽  
Tendon Organs ◽  
Group Ii Afferents

Strong evidence that premotor interneurons provide ventral spinocerebellar tract (VSCT) neurons with feedback information on their actions on motoneurons was previously found for Ia inhibitory interneurons and Renshaw cells, while indications for similar actions of other premotor interneurons were weaker and indirect. Therefore the aim of the present study was to reexamine this possibility with respect to interneurons relaying actions of group Ib afferents from tendon organs and group II afferents from muscle spindles. In all, 133 VSCT neurons in the L3–L5 segments (including 41 spinal border neurons) were recorded from intracellularly in deeply anesthetized cats to verify that stimuli applied in motor nuclei evoked monosynaptic inhibitory postsynaptic potentials (IPSPs) attributable to stimulation of axon collaterals of premotor interneurons. IPSPs were found in over two thirds of the investigated neurons. When intraspinal stimuli were preceded by stimuli applied to a muscle nerve at critical intervals, IPSPs evoked from motor nuclei were considerably reduced, indicating a collision of nerve volleys in axons of interneurons activated by group I and group II afferents. In individual VSCT neurons monosynaptic IPSPs were evoked from both biceps–semitendinosus and gastrocnemius–soleus motor nuclei, in parallel with disynaptic IPSPs from group Ib and group II as well as group Ia afferents. These observations indicate that individual VSCT neurons may monitor the degree of inhibition of both flexor and extensor motoneurons by premotor interneurons in inhibitory pathways from group Ib and group II afferents to motoneurons. They may thus be providing the cerebellum with feedback information on actions of these premotor interneurons on motoneurons.

Location and morphology of dorsal spinocerebellar tract neurons that receive monosynaptic afferent input from ankle extensor muscles in cat hindlimb

1990 ◽  
Vol 63 (2) ◽  
pp. 286-293 ◽  
Author(s):  
B. Walmsley ◽  
M. J. Nicol
Keyword(s):  
Afferent Input ◽  
Cross Sectional ◽  
Dendritic Trees ◽  
Root Entry Zone ◽  
Group I ◽  
Extensor Muscles ◽  
Dorsal Columns ◽  
Previous Proposal ◽  
Spinocerebellar Tract ◽  
Clarke's Column

1. The present experiments were carried out to investigate the morphology and somatotopic location of dorsal spinocerebellar tract (DSCT) neurons that receive monosynaptic group 1 afferent input from hindlimb ankle extensor muscles in the cat. 2. Intracellular recordings were obtained from DSCT neurons throughout the rostrocaudal extent of the L3 dorsal root entry zone of the spinal cord. DSCT neurons, physiologically identified as receiving monosynaptic group I input from the ankle extensor muscles, were injected with horseradish peroxidase (HRP) and subsequently reconstructed under the light microscope. 3. In contrast to previous HRP studies of DSCT neurons, these cells were found to have extremely extensive and complex dendritic trees, that often extend beyond the region of Clarke's column. Dendrites were found to extend into the white matter of the dorsal columns, and/or into the spinal gray matter in a ventrolateral direction. The large dendritic spread of DSCT neurons was found to occupy up to 60% or more of the cross-sectional area of Clarke's column. 4. DSCT neurons receiving monosynaptic group I input from the single functional group of ankle extensor muscles were not found to be confined within a specific transverse region of Clarke's column, in contrast to a previous proposal. Instead, these cells could be found throughout Clarke's column. 5. The present results demonstrate that DSCT neurons, physiologically identified as receiving group I muscle afferent input, exhibit dendritic trees that are considerably more extensive and morphologically complex than indicated by previous studies. In addition, the present results do not support a previous proposal of a strict somatotopic arrangement for DSCT neurons and their dendritic envelopes within Clarke's column in the transverse plane.

Ultrastructural Lesions Produced by Alcohol and Sucrose in the Heart and Liver of C57BL Mice

1970 ◽  
Vol 28 ◽  
pp. 208-209
Author(s):  
K.K. SEKHRI ◽  
C.S. ALEXANDER ◽  
H.T. NAGASAWA
Keyword(s):  
Osmium Tetroxide ◽  
Male Mice ◽  
Alcohol Group ◽  
Group Iii ◽  
Group I ◽  
C57bl Mice ◽  
Group Ii

C57BL male mice (Jackson Lab., Bar Harbor, Maine) weighing about 18 gms were randomly divided into three groups: group I was fed sweetened liquid alcohol diet (modified Schenkl) in which 36% of the calories were derived from alcohol; group II was maintained on a similar diet but alcohol was isocalorically substituted by sucrose; group III was fed regular mouse chow ad lib for five months. Liver and heart tissues were fixed in 2.5% cacodylate buffered glutaraldehyde, post-fixed in 2% osmium tetroxide and embedded in Epon-araldite.

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