==================================BSR36==================================
36. Dendritic potentials in cat spinal cord motor neurons.
1
UI - 87077614
AU - Zhang L ; Krnjevi:c K
TI - Effects of 4-aminopyridine on the action potential and the
after-hyperpolarization of cat spinal motoneurons.
AB - In cats under pentobarbital anaesthesia, intramotoneuronal
administrations of 4-aminopyridine significantly prolong the falling
phase of the antidromic action potential but have much less effect on the
orthodromic action potential. 4-aminopyridine probably blocks the fast K
channels involved in the repolarization of the membrane and indirectly
activates ionic channels through enhancement of synaptic transmission,
also suggested by the potentiation of excitatory postsynaptic potentials.
In many cells, 4-aminopyridine depresses the amplitude and prolongs the
time course of the after-hyperpolarization; therefore 4-aminopyridine may
also partly block Ca2+-activated K+ channels.
MH - Action Potentials/DRUG EFFECTS ; Aminopyridines/*PHARMACODYNAMICS ;
Animal ; Calcium/PHYSIOLOGY ; Cats ; Ion Channels/*DRUG EFFECTS ;
Membrane Potentials ; Motor Neurons/*DRUG EFFECTS ; Potassium/
PHARMACODYNAMICS ; Spinal Cord ; Support, Non-U.S. Gov't
SO - Can J Physiol Pharmacol 1986 Nov;64(11):1402-6
2
UI - 87060013
AU - Gustafsson B ; Pinter MJ ; Wigstr:om H
TI - The effect of axotomy on posttetanic potentiation of group Ia synapses in
the cat.
AB - Posttetanic potentiation (PTP) of composite Ia excitatory postsynaptic
potentials (EPSPs) has been studied in normal cat alpha-motoneurons and
in motoneurons axotomized 2-3 wk earlier by ventral root section. The
maximal amount of PTP of EPSP amplitude (expressed relative to
unpotentiated amplitude) was considerably less in the axotomized
population compared with the normal population. The decrease in PTP
provoked by axotomy occurs in association with a postaxotomy increase of
input resistance, the net effect being that PTP in axotomized cells was
much the same as that observed by others in normal motoneurons possessing
similarly high input resistance. In agreement with previous results, EPSP
peak amplitudes were decreased after axotomy. This decrease seemed to be
largely related to an absence of the largest EPSPs, since otherwise the
EPSP distributions of normal and axotomized motoneurons showed
considerable overlap. It is suggested that the observed decrease in PTP
after axotomy is related to a change in synaptic release properties and
not secondary to changes in the electrical properties of motoneurons. A
previous analysis has suggested that axotomy causes an alteration of the
distribution of passive electrical properties among motoneurons such that
axotomized cells resemble normal high-resistance motoneurons. The present
results suggest that axotomy may affect the distribution of Ia synaptic
release properties in a similar manner, since PTP in axotomized
motoneurons resembles that observed in normal high-resistance
motoneurons.
MH - Animal ; Anterior Horn Cells/PHYSIOLOGY ; Cats ; Cell Membrane/PHYSIOLOGY
; Electric Conductivity ; Membrane Potentials ; *Neural Transmission ;
Neurons, Afferent/PHYSIOLOGY ; Spinal Cord/*PHYSIOLOGY ; Support,
Non-U.S. Gov't ; Synapses/PHYSIOLOGY
SO - J Neurophysiol 1986 Oct;56(4):1174-84
3
UI - 87054482
AU - Shin HK ; Kim J ; Nam SC ; Paik KS ; Chung JM
TI - Spinal entry route for ventral root afferent fibers in the cat.
AB - Twelve anesthetized and paralyzed cats were used to study the spinal
entry routes of ventral root afferent fibers. In all animals, the spinal
cord was transected at two different levels, L5 and S2. The L5 through S2
dorsal roots were cut bilaterally, making spinal cord segments L5-S2
neurally isolated from the body except for the L5-S2 ventral roots. From
this preparation, a powerful excitation of the discharge rate of motor
neurons and dorsal horn cells within the isolated spinal segments was
observed after intraarterial injection of bradykinin (50 micrograms in
0.5 ml saline). This excitation of the spinal neurons can be considered
the most convincing evidence of the potential physiologic role of the
ventral root afferent fibers entering the spinal cord directly through
the ventral root, because the apparent route of neuronal input from the
periphery is through the ventral roots. However, additional control
experiments conducted in the present study showed that the excitation
persisted even after cutting all ventral roots within the isolated spinal
segments, indicating that excitation was not mediated by the ventral
roots. Furthermore, direct application of bradykinin on the dorsal
surface of the spinal cord also increased the motoneuronal discharge
rate, suggesting that excitation of spinal neurons produced by
intraarterial injection of bradykinin is due to a direct action of
bradykinin on the spinal cord. Thus, we provided an alternate explanation
for the most convincing evidence indicating that physiologically
important ventral root afferent fibers enter the spinal cord directly
through the ventral root. Based on existing experimental evidence, it is
likely that the majority of physiologically active ventral root afferent
fibers travel distally toward the dorsal root ganglion and then enter the
spinal cord through the dorsal root.
MH - Action Potentials/DRUG EFFECTS ; Afferent Pathways/DRUG EFFECTS/
*PHYSIOLOGY ; Animal ; Bradykinin/PHARMACODYNAMICS ; Cats ; Female ;
Ganglia, Spinal/PHYSIOLOGY ; Male ; Motor Neurons/DRUG EFFECTS/
*PHYSIOLOGY ; Neurons, Afferent/DRUG EFFECTS/PHYSIOLOGY ; Spinal Cord/
*PHYSIOLOGY ; Spinal Nerve Roots/*PHYSIOLOGY ; Support, U.S. Gov't,
P.H.S.
SO - Exp Neurol 1986 Dec;94(3):714-25
4
UI - 87027454
AU - Davies J ; Evans RH ; Herrling PL ; Jones AW ; Olverman HJ ; Pook P ;
Watkins JC
TI - CPP, a new potent and selective NMDA antagonist. Depression of central
neuron responses, affinity for [3H]D-AP5 binding sites on brain membranes
and anticonvulsant activity.
AB - Properties of a new potent antagonist acting selectively at
N-methyl-D-aspartate (NMDA) type excitatory amino acid receptors are
described. This compound,
3-((+/-)-2-carboxypiperazin-4-yl)propyl-1-phosphonic acid (CPP) is more
potent than all previously reported NMDA antagonists in depressing
mammalian spinal neuronal responses (cat and immature rat), in its
affinity for [3H]D-AP5 (a radiolabelled NMDA antagonist) binding sites on
rat brain membranes, and as an anticonvulsant in mice.
MH - Animal ; *Anticonvulsants ; Aspartic Acid/*ANALOGS & DERIVATIVES/
ANTAGONISTS & INHIBITORS ; Binding Sites ; Brain/DRUG EFFECTS/METABOLISM/
*PHYSIOLOGY ; Cats ; Cell Membrane/METABOLISM ; Interneurons/PHYSIOLOGY ;
Membrane Potentials/DRUG EFFECTS ; Mice ; Motor Neurons/PHYSIOLOGY ;
Neurons/DRUG EFFECTS/*PHYSIOLOGY ; Piperazines/*PHARMACODYNAMICS ; Rats ;
Spinal Cord/DRUG EFFECTS/*PHYSIOLOGY ; Support, Non-U.S. Gov't ; Valine/
*ANALOGS & DERIVATIVES/METABOLISM
SO - Brain Res 1986 Sep 10;382(1):169-73
5
UI - 86297538
AU - Botterman BR ; Cope TC
TI - Discharge properties of motoneurons supplying distal forelimb muscles in
the cat.
AB - Discharge properties of cat cervical motoneurons innervating distal
forelimb muscles were investigated by intracellular current injection.
Values for rheobase current, afterhyperpolarization duration and several
measures of repetitive discharge characteristics were in most respects
similar to those obtained for hindlimb motoneurons.
MH - Action Potentials ; Animal ; Cats ; Electric Stimulation ; Forelimb/
*INNERVATION/PHYSIOLOGY ; Motor Neurons/CLASSIFICATION/*PHYSIOLOGY ;
Muscles/*INNERVATION/PHYSIOLOGY ; Reaction Time/PHYSIOLOGY ; Spinal Cord/
*PHYSIOLOGY ; Ulnar Nerve/PHYSIOLOGY
SO - Brain Res 1986 Jul 30;379(1):192-5
6
UI - 86297526
AU - Yamaguchi T
TI - Descending pathways eliciting forelimb stepping in the lateral funiculus:
experimental studies with stimulation and lesion of the cervical cord in
decerebrate cats.
AB - The funicular pathways that elicit forelimb stepping were investigated
with stimulation and lesion of the cervical white matter in decerebrate
cats with the lower thoracic cord transected. We localized
cross-sectional areas where stimulation evoked rhythmic motor-nerve
discharges imitating those of stepping (fictive locomotion) in the
immobilized animal, and further examined whether or not lesions made in
the corresponding areas abolished actual locomotor movements. Stimulation
of the C3 lateral funiculus (LF) produced fictive locomotion in the
ipsilateral forelimb. The effective areas of stimulation were located
separately in the dorsolateral funiculus (DLF) and in the ventrolateral
funiculus (VLF), while the VLF was more effective than the DLF. Effective
stimuli were pulse trains with a frequency of about 30 Hz, with a rather
wide pulse duration of about 0.5 ms. Blocking axonal conduction through
the lower thoracic cord by cooling reproducibly facilitated fictive
locomotion in both amplitude and frequency. In the lesion experiments,
forelimb locomotor movements were elicited spontaneously or by
stimulation of the mesencephalic locomotor region (MLR). The locomotor
movements were abolished by complete lesions of the C2-C3 LFs on both
sides, but these remained when either the DLF or the VLF was intact on
one side. These findings together suggested that the descending pathways
for the activation of the spinal locomotor network of the single forelimb
are located ipsilaterally in the DLF as well as in the VLF. Both the DLF
and the VLF pathways can initiate locomotion, while the VLF pathways have
a higher potential for its initiation. Lesion experiments further showed
that cats can walk with both forelimbs, even though the spinal locomotor
network of the single forelimb was deprived of its main descending input
by unilateral lesions of the LF. However, when the unilateral lesion
extended to the medial part of the LF, the bilateral walking was
abolished; the limb on the lesioned side showed only rhythmic extension
movements without active flexion movements, which was out of phase with
the stepping movements on the intact side. This finding suggested that
the medial part of the LF is important for producing flexion movements
during the swing phase of stepping.
MH - Animal ; Cats ; Decerebrate State/*PHYSIOPATHOLOGY ; Efferent Pathways/
PHYSIOLOGY ; Electric Stimulation ; Evoked Potentials ; Forelimb/
*INNERVATION/PHYSIOLOGY ; Laterality/PHYSIOLOGY ; *Locomotion ; Motor
Neurons/PHYSIOLOGY ; Spinal Cord/ANATOMY & HISTOLOGY/*PHYSIOLOGY
SO - Brain Res 1986 Jul 30;379(1):125-36
7
UI - 86271071
AU - Schomburg ED ; Steffens H ; Warneke G
TI - Functional organization of the spinal reflex pathways from forelimb
afferents to hindlimb motoneurones in the cat. II. Conditions of the
interneuronal connections.
AB - The interneuronal conditions of the descending pathways from forelimb
afferents to hindlimb motoneurones were investigated by testing spatial
interactions in these pathways and between these pathways and segmental
lumbar reflex pathways. In high spinal unanaesthetized cats hindlimb
motoneurones were intracellularly recorded and spatial interactions were
tested between effects evoked by stimulation of pairs of ipsi- and
contralateral forelimb nerves or pairs of a forelimb and an ipsilateral
hindlimb nerve. The excitatory and late inhibitory pathways from forelimb
afferents projecting to most of the hindlimb motoneurone pools, showed an
interactive pattern which was distinctly different to the fast inhibitory
pathway projecting specifically from ipsilateral forelimb afferents to
flexor digitorum and hallucis longus (FDHL) motoneurones. Stimulation of
homonymous or heteronymous pairs of two forelimb nerves of both sides
evoked generally a distinct spatial facilitation of the excitatory and
late inhibitory effects, while the specific early IPSPs to FDHL
motoneurones were not facilitated. Paired stimulation of two forelimb
nerves of one side only produced spatial facilitation of EPSPs or late
IPSPs if low strength stimuli were used, using higher strength which
induced larger effects, generally caused occlusion instead. In case of
large IPSPs this may be due to the vicinity to the equilibrium potential.
Except for an inhibition of cutaneous reflex pathways, the spatial
interaction of the excitatory and late inhibitory pathways onto segmental
lumbar reflex pathways was weak and variable. The fast inhibitory pathway
to FDHL motoneurones showed a partial spatial facilitatory interaction
with lumbar reflex pathways from cutaneous and group II muscle afferents.
The second IPSP wave evoked by this pathway was inhibited by antidromic
stimulation of the ventral root L7S1 and of the alpha-efferents of the
antagonistic peroneal nerve. From the results conclusions are drawn on
the interneuronal organization of the descending pathways from forelimb
afferents to hindlimb motoneurones.
MH - Animal ; Cats ; Evoked Potentials ; Forelimb/INNERVATION ; Hindlimb/
INNERVATION ; Interneurons/PHYSIOLOGY ; Motor Neurons/*PHYSIOLOGY ;
Neural Pathways/PHYSIOLOGY ; Neural Transmission ; Neurons, Afferent/
PHYSIOLOGY ; Reflex/*PHYSIOLOGY ; Spinal Cord/*PHYSIOLOGY ; Support,
Non-U.S. Gov't
SO - Brain Res 1986 Jun 11;375(2):280-90
8
UI - 86198850
AU - Munson JB ; Foehring RC ; Lofton SA ; Zengel JE ; Sypert GW
TI - Plasticity of medial gastrocnemius motor units following cordotomy in the
cat.
AB - Experiments were performed in adult cats to determine the effects of
lumbar cordotomy on synaptic potentials, motoneuron membrane electrical
properties, muscle-unit contractile properties, and whole-muscle
histochemical properties of a heterogeneous skeletal muscle. Medial
gastrocnemius (MG) motor units were examined 1 wk to 7 mo following
complete transection of the lumbar spinal cord (cordotomy). Motor units
were classified on the basis of their contractile properties as type FF,
FI, FR, or S (8, 68). Muscle fibers were classified as type FG, FOG, or
SO on the basis of histochemical staining (59). Motoneuron electrical
properties (axonal conduction velocity, action-potential amplitude,
rheobase, input resistance, afterhyperpolarization), group I EPSPs, and
muscle-unit contractile properties (unpotentiated and potentiated twitch,
unfused and fused tetanus, fatigability) were measured. Reduced numbers
of type FR motor units and increased numbers of types FI + FF motor units
were found in electrophysiological experiments 2 wk to 7 mo following
cordotomy. Corroborative data were obtained from histochemical studies of
the same MG muscles. Electrical properties of the motoneurons of each
motor-unit type were normal following cordotomy. The close correspondence
between motoneuron electrical properties and muscle-unit contractile
properties found in normal MG muscle (68) was preserved following
cordotomy. Contractile strength of muscle units of all types was severely
reduced following cordotomy; partial recovery occurred 4-7 mo following
cordotomy. Cross-sectional area of muscle fibers was reduced at all times
investigated (2 wk to 7 mo). In three cats, homonymous group Ia
single-fiber-motoneuron EPSPs were studied 1 or 2 mo following cordotomy
at spinal level L4-5 or L5. EPSP amplitude and afferent-to-motoneuron
projection frequency were normal. In 12 other cats, composite
heteronymous group I EPSPs were studied 2 wk to 7 mo following cordotomy
at various levels. Amplitude of these EPSPs was increased, dependent upon
level of cordotomy and postoperative time. Hypotheses concerning the
influence of motoneurons on muscle, and of muscle on motoneurons, are
presented as possible mechanisms whereby the close relation between
motoneuron electrical and muscle-unit contractile properties is preserved
in the face of redistributed motor-unit populations.
MH - Afferent Pathways/PHYSIOLOGY ; Animal ; Cats ; Evoked Potentials ; Motor
Neurons/*PHYSIOLOGY ; Muscles/CYTOLOGY/*INNERVATION ; *Neuronal
Plasticity ; Spinal Cord/*PHYSIOLOGY ; Support, U.S. Gov't, Non-P.H.S. ;
Support, U.S. Gov't, P.H.S. ; Synapses/PHYSIOLOGY
SO - J Neurophysiol 1986 Apr;55(4):619-34
9
UI - 86170699
AU - Sedivec MJ ; Capowski JJ ; Mendell LM
TI - Morphology of HRP-injected spinocervical tract neurons: effect of dorsal
rhizotomy.
AB - Twenty-five physiologically identified spinocervical tract (SCT) neurons
in the sixth lumbar segment of the cat were filled with HRP by
intracellular injection. All were reconstructed from sagittal sections
using the camera lucida, and a subset (n = 18) was also reconstructed
using a computer reconstruction system. Thirteen cells were in intact
preparations, nine were in spared root preparations (L5, L6, S1, S2 cut;
L7 spared), and three were in preparations with L5 through S2 cut.
Analysis of the dendritic tree of these neurons revealed little change in
gross morphology after partial deafferentation despite increased
proportions sensitive to nociceptive input (Sedivec et al., 1983). The
dendrites still largely respected the lamina II-III border, and
relatively few dendrites were directed ventrally from the cell body,
although the ratio of ventral to dorsal dendrites was greater than
normal. The major change was an increase in surface area and volume
caused by changes in diameter (but not length) of the dendrites.
Larger-than-usual maximum branch order of individual dendritic trees of
some cells was also observed after chronic deafferentation. Thus, SCT
cells in deafferented segments do not undergo atrophy, but show, rather,
limited signs of growth and the possibility of dendritic reorganization.
We have also computed correlations between different parameters of these
cells (cell body size, number and size of primary dendrites, total area
and length of individual dendrites) and have found that, as in
motoneurons, diameter of the primary dendrite measured 30 micron from the
soma is significantly correlated with total dendritic surface area and
length. SCT neurons tend to have more dendrites than spinal
alpha-motoneurons, but total surface area is smaller for a given diameter
of a proximal dendrite.
MH - Animal ; Cats ; Computers ; Dendrites/CYTOLOGY ; Female ; Horseradish
Peroxidase/METABOLISM ; Male ; Mathematics ; Motor Neurons/CYTOLOGY ;
Neurons/*CYTOLOGY ; Spinal Nerve Roots/*PHYSIOLOGY ; Spinothalamic Tracts/
*CYTOLOGY ; Support, U.S. Gov't, P.H.S.
SO - J Neurosci 1986 Mar;6(3):661-72
10
UI - 86170690
AU - Vanden Noven S ; Hamm TM ; Stuart DG
TI - Partitioning of monosynaptic Ia excitatory postsynaptic potentials in the
motor nucleus of the cat lateral gastrocnemius muscle.
AB - Experiments were conducted to test the hypothesis that a partitioning of
Ia monosynaptic excitatory postsynaptic potentials (Ia EPSPs) is present
in motor nuclei supplying muscles with regions capable of different
mechanical actions. Intracellular recordings of synaptic potentials were
made in lateral gastrocnemius (LG) motoneurons in anesthetized low-spinal
cats. The effects were tested of stimuli (group I range) to the four
primary nerve branches of the LG nerve supplying muscle compartments LGm,
LG1, LG2, and LG3 (terminology of English, Ref. 26) and the nerve to a
heteronymous muscle, soleus. Stimulation of a given LG nerve branch
produced monosynaptic Ia EPSPs of greater amplitude in "own-branch:
motoneurons than "other-branch: cells. A significant partitioning of mean
Ia EPSPs was found in three (LG1, LG2, LG3) out of the four homonymous
pathways studied. An EPSP normalization (7) was performed to eliminate
potential differences in cell type that might affect the amplitudes of
the EPSPs between these four cell groups (e.g., differences in the number
of cells supplying FF, FR, and S muscle units). This normalization
confirmed that the partitioning of monosynaptic Ia inputs upon
stimulation of LG1, LG2, and LG3 could not be attributed to differences
in cell type. In addition, the effects of LGm stimulation were found to
be significantly greater in the LGm motoneurons compared with the other
cell groups. Heteronymous input (from soleus) to the LG motor nucleus
showed some partitioned effects. Motoneurons innervating compartment LG2
received larger EPSPs from soleus than did the cells supplying
compartments LG1, LG3, and LGm. The contributions of location specificity
and species specificity (terminology of Scott and Mendell, Ref. 55) in
the establishment of these Ia-afferent-motoneuronal connections were
examined. Cell location sites within the spinal cord were consistent with
location specificity making some contribution to the observed pattern of
homonymous Ia connections. A more prominent role for species specificity
was indicated by species-dependent differences in EPSP amplitude in pairs
of LG motoneurons (e.g., LGm vs. LG2) at similar rostrocaudal locations
upon stimulation of a given homonymous or heteronymous nerve/branch.
MH - Afferent Pathways/PHYSIOLOGY ; Animal ; Cats ; Electric Stimulation ;
Electrophysiology ; Evoked Potentials ; Models, Neurological ; Motor
Neurons/*PHYSIOLOGY ; Muscles/*INNERVATION ; Review ; Spinal Cord/
PHYSIOLOGY ; Support, Non-U.S. Gov't ; Support, U.S. Gov't, P.H.S. ;
Synapses/PHYSIOLOGY
SO - J Neurophysiol 1986 Mar;55(3):569-86
11
UI - 86170681
AU - Shinoda Y ; Yamaguchi T ; Futami T
TI - Multiple axon collaterals of single corticospinal axons in the cat spinal
cord.
AB - To investigate intraspinal branching patterns of single corticospinal
neurons (CSNs), we recorded extracellular spike activities from cell
bodies of 408 CSNs in the motor cortex in anesthetized cats and mapped
the distribution of effective stimulating sites for antidromic activation
of their terminal branches in the spinal gray matter. To search for all
spinal axon branches belonging to single CSNs in the "forelimb area: of
the motor cortex, we microstimulated the gray matter from the dorsal to
the ventral border at 100-micron intervals at an intensity of 150-250
microA and systematically mapped effective stimulating penetrations at
1-mm intervals rostrocaudally from C3 to the most caudal level of their
axons. From the depth-threshold curves, the comparison of the antidromic
latencies of spikes evoked from the gray matter and the lateral
funiculus, and the calculated conduction times of the collaterals, we
could ascertain that axon collaterals were stimulated in the gray matter
rather than stem axons in the corticospinal tract due to current spread.
Virtually all CSNs examined in the forelimb area of the motor cortex had
three to seven branches at widely separated segments of the cervical and
the higher thoracic cord. In addition to terminating at the brachial
segments, they had one to three collaterals to the upper cervical cord
(C3-C4), where the propriospinal neurons projecting to forelimb
motoneurons are located. About three quarters of these CSNs had two to
four collaterals in C6-T1. This finding held true for both fast and slow
CSNs. About one third of the CSNs in the forelimb area of the motor
cortex projected to the thoracic cord below T3. These CSNs also sent axon
collaterals to the cervical spinal cord. CSNs in the "hindlimb area: of
the motor cortex had three to five axon branches in the lumbosacral cord.
These branches were mainly observed at L4 and the lower lumbosacral cord.
None of these CSNs had axon collaterals in the cervical cord. CSNs
terminating at different segments of the cervical and the thoracic cord
were distributed in a wide area of the motor cortex and were
intermingled. To determine the detailed trajectory of single axon
branches, microstimulation was made at a matrix of points of 100 or 200
micron at the maximum intensity of 30 microA, and their axonal trajectory
was reconstructed on the basis of the location of low-threshold foci and
the latency of antidromic spikes.(ABSTRACT TRUNCATED AT 400 WORDS)
MH - Animal ; Axons/*PHYSIOLOGY/ULTRASTRUCTURE ; Cats ; Electric Stimulation ;
Electrophysiology ; Evoked Potentials ; Interneurons/PHYSIOLOGY/
ULTRASTRUCTURE ; Motor Cortex/PHYSIOLOGY/ULTRASTRUCTURE ; Motor Neurons/
PHYSIOLOGY/ULTRASTRUCTURE ; Review ; Spinal Cord/*PHYSIOLOGY/
ULTRASTRUCTURE ; Support, Non-U.S. Gov't
SO - J Neurophysiol 1986 Mar;55(3):425-48
12
UI - 86169025
AU - Wong-Riley MT ; Kageyama GH
TI - Localization of cytochrome oxidase in the mammalian spinal cord and
dorsal root ganglia, with quantitative analysis of ventral horn cells in
monkeys.
AB - The spinal cord and dorsal root ganglia of mice, rats, cats, squirrel
monkeys, and macaque monkeys were examined at both the light and electron
microscopic levels for cytochrome oxidase activity. A similar
histochemical pattern prevailed in all of the species examined. While the
spinal gray exhibited a heterogeneous but consistent distribution of the
enzyme, the white matter was only lightly stained. Highly reactive
neurons were either singly scattered or aggregated into discrete
clusters. The dorsal nucleus of Clarke, the lateral cervical nucleus
(cat), the intermediolateral cell columns of the thoracic and upper
lumbar levels, and selected groups of ventral horn neurons formed
moderate to darkly reactive cell clusters, whereas fusiform and
multipolar cells of Waldeyer in the marginal layer, small fusiform
neurons in the ventral gray, funicular cells in the white matter, and
ventral horn neurons of varying sizes tended to stand out against the
neuropil as singly reactive neurons. At the electron microscopic level,
reactive neurons were characterized by a greater packing density of
darkly reactive mitochondria, while lightly reactive ones had fewer
mitochondria, most of which showed very little reaction product. Reactive
mitochondria were also found in the neuropil, mainly in dendritic
profiles and some axon terminals. Glial cells, in general, were not very
reactive. Ventral horn neurons from three macaque monkeys were measured
for somatic areas and optical densities of cytochrome oxidase reaction
product. A total of 1,770 neurons from representative sections of the
cervical, thoracic, lumbar, and sacral cords of these animals were
analyzed. The results indicated that the distribution of cell sizes as
well as optical densities at every level of the cord fell on a continuum.
Analysis of the regression coefficients revealed that the slopes were
negative for all levels, indicating that there was a general inverse
relationship between cell size and optical densities. However, there were
representations of dark, moderate, and lightly reactive neurons in all
three size categories (large, medium, and small). Thus, the level of
oxidative metabolism of ventral horn neurons cannot be correlated
strictly with size, but it is likely to reflect their total synaptic and
spontaneous activities. Neurons of the dorsal root ganglia likewise
exhibited heterogeneous distribution of cell sizes and levels of enzyme
reactivity, while satellite cells, in general, were only lightly
reactive. As in the case of the ventral horn, representatives of dark,
moderate, and light levels of reactivity occurred in every size category
of neurons.(ABSTRACT TRUNCATED AT 400 WORDS)
MH - Animal ; Cats ; Cytochrome Oxidase/*ANALYSIS ; Densitometry ; Ganglia,
Spinal/*ENZYMOLOGY/ULTRASTRUCTURE ; Macaca fascicularis ; Macaca mulatta
; Mice ; Microscopy, Electron ; Motor Neurons/CLASSIFICATION/CYTOLOGY ;
Neurons/*ENZYMOLOGY/ULTRASTRUCTURE ; Rats ; Spinal Cord/*ENZYMOLOGY/
ULTRASTRUCTURE ; Stains and Staining ; Support, U.S. Gov't, P.H.S.
SO - J Comp Neurol 1986 Mar 1;245(1):41-61
13
UI - 86164763
AU - Henatsch HD ; Meyer-Lohmann J ; Windhorst U ; Schmidt J
TI - Differential effects of stimulation of the cat's red nucleus on lumbar
alpha motoneurones and their Renshaw cells.
AB - The red nucleus region was stereotaxically stimulated with short trains
of high-frequency alternating current pulses in anaesthetized cats. The
effects were studied, in contralateral lumbar segments, on the responses
of microrecorded individual Renshaw cells (RCs) to antidromic or
orthodromic test shocks of ventral root or muscle nerve fibres.
Monosynaptic reflexes (MRs) of their motoneurone pools were recorded from
one of the cut lumbar ventral roots. Averages of 10-20 replicate test
responses of the RC (converted into instantaneous frequency curves, IFCs)
and of the MR shapes were computed and graphically displayed. 2.
Orthodromic (afferent) test shocks induced simultaneously MRs as well as
responses of a RC belonging to the same motor pool. From their paired
records at systematically varied shock strengths, whole "linkage
characteristics: of the relation between the two events could be
obtained, representing the functional linkage from the motoraxon
collaterals to the RC under study. The overall result of rubral
conditioning was a change in the course of the characteristic, which
indicated a reduction of this linkage (= relative inhibition of the RC
against its recurrent input). 3. Sequential trials with test shocks of
constant, submaximal strength were performed with 45 individual RCs. The
clearest results were obtained with RC responses to antidromic ventral
root shocks: 65% of the RCs were partially inhibited by rubral
conditioning. Interposed minor facilitory subcomponents could be seen in
the course of inhibited IFCs. Mixed sequences of manifest
inhibitory/facilitory effects were observed in 11%; reversed sequences
(facilitory/inhibitory) did not occur. A pure but weak facilitation was
found in only one case, paralleled by an increase of the MR. RCs
belonging to either extensor or flexor motor pools were affected about
equally. A little over 20% of the tested RCs remained uninfluenced by
rubral stimulation. 4. The MRs, induced by constant, submaximal,
orthodromic test shocks, were usually enhanced with only few exceptions,
by rubral stimulation. The effects on the orthodromic RC responses were
mainly inhibitory, but could be more or less masked by the concurrent
increase of the MR, providing a stronger recurrent input to the RC. Such
inhibition could be uncovered, however, by observing the above described
linkage change. 5. Variation of several parameters of rubral conditioning
(train duration, timing of train with respect to test shock, strength of
train) modified the inhibitory effects on antidromic RC responses to a
certain extent without changing their principal character.(ABSTRACT
TRUNCATED AT 400 WORDS)
MH - Animal ; Brain Mapping ; Cats ; Electric Stimulation ; Evoked Potentials
; Extrapyramidal Tracts/PHYSIOLOGY ; Interneurons/PHYSIOLOGY ; Motor
Neurons/PHYSIOLOGY ; Neural Inhibition ; Red Nucleus/*PHYSIOLOGY ;
Reflex, Monosynaptic ; Spinal Cord/*PHYSIOLOGY ; Support, Non-U.S. Gov't
SO - Exp Brain Res 1986;62(1):161-74
14
UI - 86136409
AU - Edgley S ; Jankowska E ; McCrea D
TI - The heteronymous monosynaptic actions of triceps surae group Ia afferents
on hip and knee extensor motoneurones in the cat.
AB - Monosynaptic connections from the group Ia afferents of triceps surae
onto quadriceps, anterior biceps and semimembranosus motoneurones have
been demonstrated in the cat. They appear to be equivalent to those found
between triceps surae and thigh muscles in man.
MH - Animal ; Cats ; Comparative Study ; Evoked Potentials ; Leg ; Motor
Neurons/*PHYSIOLOGY ; Muscles/*INNERVATION ; Neural Transmission ;
Neurons, Afferent/PHYSIOLOGY ; Organ Specificity ; Spinal Cord/
*PHYSIOLOGY ; Support, Non-U.S. Gov't ; Synapses/PHYSIOLOGY
SO - Exp Brain Res 1986;61(2):443-6
15
UI - 86136394
AU - Lipski J ; Bektas A ; Porter R
TI - Short latency inputs to phrenic motoneurones from the sensorimotor cortex
in the cat.
AB - Short latency responses were recorded from C5 phrenic roots and
intracellularly from phrenic motoneurones following stimulation of the
pericruciate cortex or medullary pyramids in cats anaesthetized with
Nembutal or chloralose-urethane. Focal stimulation of the cortical
surface (single pulses, 0.5-2 ms, 0.3-8 mA) during inspiration evoked
EPSPs (latency 4.7 +/- 1.7 ms, rise time 1.9 +/- 1.1 ms, amplitude 0.22
to 3.94 mV) in 42% of motoneurones studied (n = 107). The EPSPs were
absent, or on average 60% smaller, following stimulation during
expiration. In all but two motoneurones, during both inspiration and
expiration, hyperpolarizing potentials were observed either following the
initial depolarization or alone. They could be reversed by
hyperpolarizing current or chloride injection. Stimulation of the
pyramidal tract at mid medullary level (1 to 3 pulses, 0.2 ms) evoked
short latency excitation in phrenic motoneurones only with currents of
more than 200 microA. Smaller stimuli applied to the medial reticular
formation above the pyramidal tract evoked excitation (onset latency
1.5-3.2 ms) in which the earliest part was probably monosynaptic. These
results show that the corticospinal responses in phrenic motoneurones are
both excitatory and inhibitory. They are not transmitted through the
pyramidal tract and are at least disynaptic. Excitation evoked from the
medullary pyramidal tract can be explained by current spread beyond the
pyramidal tract fibres.
MH - Animal ; Brain Mapping ; Cats ; Evoked Potentials ; Female ; Male ; Motor
Cortex/*PHYSIOLOGY ; Motor Neurons/*PHYSIOLOGY ; Neural Inhibition ;
Neural Transmission ; Phrenic Nerve/*PHYSIOLOGY ; Pyramidal Tracts/
PHYSIOLOGY ; Reaction Time/PHYSIOLOGY ; Reticular Formation/PHYSIOLOGY ;
Somatosensory Cortex/*PHYSIOLOGY
SO - Exp Brain Res 1986;61(2):280-90