scholarly journals Group I extensor afferents evoke disynaptic EPSPs in cat hindlimb extensor motorneurones during fictive locomotion.

1996 ◽  
Vol 494 (3) ◽  
pp. 851-861 ◽  
Author(s):  
M J Angel ◽  
P Guertin ◽  
T Jiménez ◽  
D A McCrea
Keyword(s):  
Fictive Locomotion ◽  
Group I

Effects of Ankle and Hip Muscle Afferent Inputs on Rhythm Generation During Fictive Locomotion

2010 ◽  
Vol 103 (3) ◽  
pp. 1591-1605 ◽  
Author(s):  
Alain Frigon ◽  
Jennifer Sirois ◽  
Jean-Pierre Gossard
Keyword(s):  
Rectus Femoris ◽  
Extension Phase ◽  
Cycle Period ◽  
Fictive Locomotion ◽  
Phase Duration ◽  
Locomotor Rhythm ◽  
Rhythm Generator ◽  
Hip Muscle ◽  
Group I ◽  
Group Ii

Hip position and loading of limb extensors are major sensory cues for the initiation and duration of different phases during walking. Although these inputs have pathways projecting to the locomotor rhythm generator, their effects may vary in different parts of the locomotor cycle. In the present study, the plantaris (Pl), sartorius (Sart), rectus femoris (RF), and caudal gluteal (cGlu) nerves were stimulated at group I and/or group II strength during spontaneous fictive locomotion in 16 adult decerebrate cats. These nerves supply muscles that extend the ankle (Pl), flex the hip (Sart, RF), or extend the hip (cGlu). Stimuli were given at six epochs of the locomotor cycle to evaluate when they access the rhythm generator. Group I afferents from Pl nerve always reset the locomotor rhythm; stimulation during extension prolonged cycle period and extension phase duration, while stimulation during flexion terminated flexion and initiated extension. On the other hand, stimulating RF and cGlu nerves only produced significant effects on the rhythm in precise epochs, particularly during mid-flexion and/or mid- to late extension. Stimulating the Sart nerve produced complex effects on the rhythm that were not distributed evenly to all extensor motor pools. The most consistent effect was reduced flexion phase duration with stimulation during flexion, particularly at group II strength, and prolongation of the extension phase but only in late extension. That hip muscle afferents reset the rhythm in only specific epochs of the locomotor cycle suggests that the rhythm generator operates with several subdivisions to determine phase and cycle durations.

Sensory Integration in Presynaptic Inhibitory Pathways During Fictive Locomotion in the Cat

2002 ◽  
Vol 88 (1) ◽  
pp. 163-171 ◽  
Author(s):  
Ariane Ménard ◽  
Hugues Leblond ◽  
Jean-Pierre Gossard
Keyword(s):  
Presynaptic Inhibition ◽  
Muscle Afferents ◽  
Primary Afferent Depolarization ◽  
Skin Area ◽  
Fictive Locomotion ◽  
Step Cycle ◽  
Primary Afferent ◽  
Decerebrate Cat ◽  
Group I ◽  
Group I Afferents

The aim of this study is to understand how sensory inputs of different modalities are integrated into spinal cord pathways controlling presynaptic inhibition during locomotion. Primary afferent depolarization (PAD), an estimate of presynaptic inhibition, was recorded intra-axonally in group I afferents ( n = 31) from seven hindlimb muscles in L6–S1 segments during fictive locomotion in the decerebrate cat. PADs were evoked by stimulating alternatively low-threshold afferents from a flexor nerve, a cutaneous nerve and a combination of both. The fictive step cycle was divided in five bins and PADs were averaged in each bin and their amplitude compared. PADs evoked by muscle stimuli alone showed a significant phase-dependent modulation in 20/31 group I afferents. In 12/20 afferents, the cutaneous stimuli alone evoked a phase-dependent modulation of primary afferent hyperpolarization (PAH, n = 9) or of PADs ( n = 3). Combining the two sensory modalities showed that cutaneous volleys could significantly modify the amplitude of PADs evoked by muscle stimuli in at least one part (bin) of the step cycle in 17/31 (55%) of group I afferents. The most common effect (13/17) was a decrease in the PAD amplitude by 35% on average, whereas it was increased by 17% on average in the others (4/17). Moreover, in 8/13 afferents, the PAD reduction was obtained in 4/5 bins i.e., for most of the duration of the step cycle. These effects were seen in group I afferents from all seven muscles. On the other hand, we found that different cutaneous nerves had quite different efficacy; the superficial peroneal (SP) being the most efficient (85% of trials) followed by Saphenous (60%) and caudal sural (44%) nerves. The results indicate that cutaneous interneurons may act, in part, by modulating the transmission in PAD pathways activated by group I muscle afferents. We conclude that cutaneous input, especially from the skin area on the dorsum of the paw (SP), could subtract presynaptic inhibition in some group I afferents during perturbations of stepping (e.g., hitting an obstacle) and could thus adjust the influence of proprioceptive feedback onto motoneuronal excitability.

scholarly journals Group I disynaptic excitation of cat hindlimb flexor and bifunctional motoneurones during fictive locomotion

2000 ◽  
Vol 525 (2) ◽  
pp. 549-564 ◽  
Author(s):  
J. Quevedo ◽  
B. Fedirchuk ◽  
S. Gosgnach ◽  
D. A. McCrea
Keyword(s):  
Fictive Locomotion ◽  
Group I

scholarly journals Modulation of Oligosynaptic Cutaneous and Muscle Afferent Reflex Pathways During Fictive Locomotion and Scratching in the Cat

1998 ◽  
Vol 79 (1) ◽  
pp. 447-463 ◽  
Author(s):  
A. M. Degtyarenko ◽  
E. S. Simon ◽  
T. Norden-Krichmar ◽  
R. E. Burke
Keyword(s):  
Membrane Potential ◽  
Central Pattern Generators ◽  
Muscle Afferents ◽  
Flexor Hallucis Longus ◽  
Fictive Locomotion ◽  
Postsynaptic Potentials ◽  
Cutaneous Reflex ◽  
Reflex Pathways ◽  
Group I ◽  
Muscle Afferent

Degtyarenko, A. M., E. S. Simon, T. Norden-Krichmar, and R. E. Burke. Modulation of oligosynaptic cutaneous and muscle afferent reflex pathways during fictive locomotion and scratching in the cat. J. Neurophysiol. 79: 447–463, 1998. We have compared state-dependent transmission through oligosynaptic (minimally disynaptic) reflex pathways from low-threshold cutaneous and muscle afferents to some flexor and extensor lumbosacral motoneurons during fictive locomotion and scratching in decerebrate unanesthetized cats. As reported in earlier work, oligosynaptic cutaneous excitatory postsynaptic potentials (EPSPs) in flexor digitorum longus (FDL) and inhibitory postsynaptic potentials (IPSPs) in extensor digitorum (EDL) longus motoneurons were enhanced markedly during the early flexion phase of fictive locomotion. We show in this paper that, in contrast, these cutaneous reflex pathways were depressed markedly during all phases of fictive scratching. On the other hand, disynaptic EPSPs produced by homonymous and synergist group I muscle afferents in flexor (tibialis anterior and EDL) motoneurons were present and strongly modulated during both fictive locomotion and scratching. During both actions, these disynaptic group I EPSPs appeared or exhibited the largest amplitude when the motoneuron membrane potential was most depolarized and the parent motor pool was active. There was an interesting exception to the simple pattern of coincident group I EPSP enhancement and motoneuron depolarization. During locomotion, disynaptic group I EPSPs in both FDL and flexor hallucis longus (FHL) motoneurons cells were facilitated during the extension phase, although FDL motoneurons were relatively hyperpolarized whereas FHL cells were depolarized. The reverse situation was found during fictive scratching; group I EPSPs were facilitated in both FDL and FHL cells during the flexion phase when FDL motoneurons were depolarized and FHL cells were relatively hyperpolarized. These observations suggest that the disynaptic EPSPs in these two motor nuclei are produced by common interneurons. Reciprocal disynaptic inhibitory pathways from group Ia muscle afferents to antagonist motoneurons were also active and subject to phase-dependent modulation during both fictive locomotion and scratching. In all but one cell tested, reciprocal disynaptic group Ia IPSPs were largest during those phases in which the motoneuron membrane potential was relatively hyperpolarized and the parent motor pool was inactive. Oligosynaptic PSPs in motoneurons produced by stimulation of the mesencephalic locomotor region (MLR) were modulated strongly during fictive locomotion but were suppressed powerfully throughout fictive scratching. Large cord dorsum potentials generated by MLR stimuli also were suppressed markedly during fictive scratching. These results allow certain inferences about the organization of interneurons in the pathways examined. They also suggest that the central pattern generators that produce fictive locomotion and scratching are organized differently.

An intracellular study of muscle primary afferents during fictive locomotion in the cat

1991 ◽  
Vol 65 (4) ◽  
pp. 914-926 ◽  
Author(s):  
J. P. Gossard ◽  
J. M. Cabelguen ◽  
S. Rossignol
Keyword(s):  
Muscle Spindle ◽  
Vastus Lateralis ◽  
Relative Size ◽  
Primary Afferents ◽  
Triceps Surae ◽  
Resting Potential ◽  
Fictive Locomotion ◽  
Group I ◽  
Group Ii ◽  
Bifunctional Muscle

1. Presynaptic activity of identified primary afferents from flexor, extensor, and bifunctional hindlimb muscles was studied with intra-axonal recordings during fictive locomotion. Fictive locomotion appeared spontaneously in decorticate cats (n = 9), with stimulation of the mesencephalic locomotor region (n = 4), and in spinal cats injected with clonidine or nialamide and L-DOPA (n = 4). Representative flexor and extensor muscle nerves, recorded to monitor the locomotor pattern and dorsal rootlets of the sixth and seventh lumbar segments, were recorded simultaneously to monitor dorsal root potentials (DRPs). 2. From responses to muscle stretches and, in some instances, twitch contractions of the parent muscle, 75% of the single units examined were putatively identified as spindle afferents (40/53). On the basis of conduction velocity and stimulation threshold, 73% of these were further classified as group I fibers (29/40), the rest as group II fibers. 3. All units (n = 53 with resting potential more negative than -45 mV) showed fluctuations of their membrane potential (up to 1.5 mV) at the rhythm of the fictive locomotion. Subsequent averaging of these fluctuations over several cycles revealed that 89% of all units displayed a predominant wave of depolarization during the flexor phase, followed by a trough of repolarization. In 79% of the units, there was also a second, usually smaller, depolarization during the extensor phase. The relative size of each wave of depolarization could vary with different episodes of fictive locomotion in the same unit and among various afferents from the same muscle in the same experiment. 4. The firing frequency of some afferents from the ankle flexor tibialis anterior (5/16) and the bifunctional muscle posterior biceps-semitendinosus (4/15) was phasically modulated along the fictive step cycle. The maximum frequency always occurred during the flexor phase, i.e., during the largest depolarization of the unit. Because of the absence of phasic sensory input in the curarized animal, we assume that the phasic discharges were generated within the spinal cord and antidromically propagated. Phasic firing was never encountered in afferents from extensor muscles such as triceps surae (0/15) and vastus lateralis (0/4). 5. The results demonstrate that the pattern of rhythmic depolarization accompanying fictive locomotion is similar for the majority of flexor, extensor, and bifunctional group I (and possibly group II) muscle spindle primary afferents. They further indicate that there is a specific phasic modulation of antidromic firing for some flexor and bifunctional muscle spindle afferents.(ABSTRACT TRUNCATED AT 400 WORDS)

scholarly journals Ankle extensor group I afferents excite extensors throughout the hindlimb during fictive locomotion in the cat.

1995 ◽  
Vol 487 (1) ◽  
pp. 197-209 ◽  
Author(s):  
P Guertin ◽  
M J Angel ◽  
M C Perreault ◽  
D A McCrea
Keyword(s):  
Fictive Locomotion ◽  
Group I ◽  
Group I Afferents

scholarly journals Disynaptic group I excitation of synergist ankle extensor motoneurones during fictive locomotion in the cat.

1995 ◽  
Vol 487 (2) ◽  
pp. 527-539 ◽  
Author(s):  
D A McCrea ◽  
S J Shefchyk ◽  
M J Stephens ◽  
K G Pearson
Keyword(s):  
Fictive Locomotion ◽  
Group I ◽  
Extensor Motoneurones

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.

The Quantitative Ultrastructure of the Heart Muscle of Japanese Quail by Hypergravitation, Hypodynamy and Combination

1990 ◽  
Vol 48 (3) ◽  
pp. 188-189
Author(s):  
Anton Bózner ◽  
Mikuláš Gažo ◽  
Jozef Dostál
Keyword(s):  
Japanese Quail ◽  
Heart Muscle ◽  
Relative Size ◽  
Combination Group ◽  
Control Group ◽  
Group V ◽  
Group Iii ◽  
Space Flights ◽  
Group I ◽  
Quantitative Ultrastructure

It is anticipated that Japanese quail /Coturnix coturnix japonica/ will provide animal proteins in long term space flights. Consequently this species of birds is of research interest of international space program INTERCOSMOS. In the year 1987 we reported on an experiment /2/ in which the effect of chronic acceleration of 2 G hypergravitation, the hypodynamy and the simultaneous effect of chronic acceleration and the location in the centre of the turntable of the centrifuge on the protein fractions in skeletal muscles was studied. The ultrastructure of the heart muscle was now in this experiments examined as well.Japanese quail cockerels, aged 48 days were exposed to 2 G hypergravitation /group IV/ in a 6,4 m diameter centrifuge, to hypodynamy /group III/ and their combination /group V/, respectively for 6 days / Fig.1/. The hypodynamy in group III was achieved by suspending the birds in jackets without contact the floor. The group II was located in the centre ofthe turntable of the centrifuge. The control group I. was kept under normal conditions. The quantitative ultrastructure of myocard was evaluated by the methods of Weibel/3/ - this enables to determine the number, relative size and volume of mitochondria volume of single mitochondria, defficiency of mitochondrial cristae and volume of myofibrils.

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