scholarly journals Time course and extent of recovery in reinnervated motor units of cat triceps surae muscles

1982 ◽  
Vol 323 (1) ◽  
pp. 307-323 ◽  
Author(s):  
Tessa Gordon ◽  
R. B. Stein
Keyword(s):  
Time Course ◽  
Motor Units ◽  
Triceps Surae ◽  
Triceps Surae Muscles

scholarly journals Intrinsic Properties and Reflex Compensation in Reinnervated Triceps Surae Muscles of the Cat: Effect of Activation Level

2003 ◽  
Vol 90 (3) ◽  
pp. 1537-1546 ◽  
Author(s):  
Clotilde M.J.I. Huyghues-Despointes ◽  
Timothy C. Cope ◽  
T. Richard Nichols
Keyword(s):  
Mechanical Properties ◽  
Stretch Reflex ◽  
Full Range ◽  
Motor Units ◽  
Triceps Surae ◽  
Type I ◽  
Initial Stiffness ◽  
Decerebrate Cat ◽  
Reflex Action ◽  
Triceps Surae Muscles

The manner in which activation levels influence intrinsic muscular properties and contributions of the stretch reflex were studied in homogeneous soleus (SOL) and heterogeneous gastrocnemius (G) muscles in the decerebrate cat. Intrinsic mechanical properties were represented by the initial stiffness of the muscle, measured prior to reflex action, and by the tendency of the muscle to yield during stretch in the absence of the stretch reflex. Stiffness regulation by the stretch reflex was evaluated by measuring the extent to which reflex action reduces yielding and the extent to which stiffness depends on background force. Intrinsic mechanical properties were measured in muscles deprived of effective autogenic reflexes using the method of muscular reinnervation. Reinnervated muscles were recruited to force levels comparable to those achieved during natural locomotion. As force declined during crossed-extension reflexes in reinnervated and intact muscles, initial stiffness declined according to similar convex trajectories. The data did not support the hypothesis that, for a given force level, initial stiffness is greatest in populations of predominantly type I motor units. Incremental stiffness (Δ f/Δ l) of both G and SOL increased in the presence of the stretch reflex. Yielding of SOL (ratio of incremental to initial stiffness) substantially decreased in the presence of the stretch reflex over the full range of forces. In reflexive G, yielding significantly decreased for low to intermediate forces, whereas at higher forces, yielding was similar irrespective of the presence or absence of the stretch reflex. The stretch reflex regulates stiffness in both homogeneous and heterogeneous muscles.

Comparison of physiological and histochemical properties of motor units after cross-reinnervation of antagonistic muscles in the cat hindlimb

1988 ◽  
Vol 60 (1) ◽  
pp. 365-378 ◽  
Author(s):  
T. Gordon ◽  
C. K. Thomas ◽  
R. B. Stein ◽  
S. Erdebil
Keyword(s):  
Muscle Fibers ◽  
Motor Units ◽  
Triceps Surae ◽  
Medial Gastrocnemius ◽  
Single Motor Units ◽  
Extensor Muscles ◽  
Flexor Muscles ◽  
The Cross ◽  
Triceps Surae Muscles ◽  
Fast Twitch

1. Physiological and histochemical properties of the cat ankle extensor muscles, the lateral and medial gastrocnemius, and the soleus were studied after cross-reinnervation by flexor motoneurons. 2. Tibial and common peroneal nerves were cut and cross-united in the popliteal fossa of 2- to 6-mo-old cats. Eighteen to 24 mo later, single motor units were isolated by dissection and stimulation of ventral root filaments and classified into four types: fast-twitch, fatigable (FF), fast-twitch with intermediate fatigue resistance (FI), fast-twitch, fatigue-resistant (FR), and slow, fatigue-resistant (S). Muscle fibers were classified as fast glycolytic (FG), fast, oxidative glycolytic (FOG), and slow oxidative (SO) on the basis of histochemical staining. 3. Although motor-unit force was normally well correlated with the size of the innervating motor axon in the cross-reinnervated muscles, the force of different unit types overlapped considerably. The reinnervated motor units also showed a higher than normal degree of fatigability. 4. The range of muscle unit forces in cross-reinnervated triceps surae muscles was the same as in the normally innervated triceps surae muscles. This range is 2-3 times greater than the flexor muscles, which the common peroneal nerve normally supplies. The range of contraction speed of units in the cross-reinnervated extensor muscles was comparable to that in the flexor muscles, consistent with a motoneuron-specific determination of muscle speed (28). 5. SO and FOG muscle fibers were found in all reinnervated triceps surae muscles, but FG fibers were only found in reinnervated medial gastrocnemius (MG) and lateral gastrocnemius (LG) muscles, consistent with previous findings of the resistance of soleus muscles to complete conversion (10, 16, 20, 21). Type grouping of muscle fibers was characteristic of the reinnervated muscles. 6. Reinnervated SO muscle fibers were larger than the corresponding fibers in normally innervated muscles as were the estimated number of muscle fibers innervated by slow motor axons. Nonetheless, the force generated by the S motor units remained relatively smaller than FR and FF units. The relative contributions of the number, cross-sectional area and specific tension to the force generation of reinnervated motor units are discussed.

Properties of motor units after immobilization of cat peroneus longus muscle

1993 ◽  
Vol 74 (3) ◽  
pp. 1131-1139 ◽  
Author(s):  
J. Petit ◽  
M. Gioux
Keyword(s):  
Time Course ◽  
Relaxation Times ◽  
Motor Units ◽  
Short Length ◽  
Low Frequencies ◽  
Tetanic Force ◽  
Peroneus Longus ◽  
Single Motor Units ◽  
Longus Muscle ◽  
Selective Immobilization

Changes in contractile properties of cat peroneus longus motor units were studied 2, 5, and 8 wk after selective immobilization of this muscle, which was achieved by fixing the distal tendon of the peroneus longus to the fibula either at the muscle minimal physiological length ("short" length) or at the length for a 90 degree ankle joint ("neutral" length). In each muscle, 75–90% of the units [slow (S), fast resistant to fatigue (FR), fast intermediate (FI), and fast fatigable (FF)] were studied. Immobilization elicited a permanent decrease in tetanic force developed by single motor units, which was larger for resistant-to-fatigue units (S, FR). In most instances this decrease was not related to the immobilization length. In all units, twitch contraction and half-relaxation times underwent a transient increase, the extent and time course of which were influenced by immobilization length. The relationship between the frequency of motor units activation and the ratio of unfused to maximal tetanic force was studied. For fast units, there was a transient shift of the relation toward low frequencies after 2 and 5 wk of immobilization at neutral and short length, respectively.

Dynamic Force Responses in Electrically Stimulated Triceps Surae Muscles: Effects of Fatigue and Temperature

1999 ◽  
Vol 23 (5) ◽  
pp. 436-439 ◽  
Author(s):  
Dietmar Rafolt ◽  
Eugen Gallasch ◽  
Winfried Mayr ◽  
Hermann Lanmuller
Keyword(s):  
Triceps Surae ◽  
Dynamic Force ◽  
Triceps Surae Muscles

Receptor Mechanisms Underlying Heterogenic Reflexes Among the Triceps Surae Muscles of the Cat

1999 ◽  
Vol 81 (2) ◽  
pp. 467-478 ◽  
Author(s):  
T. Richard Nichols
Keyword(s):  
Triceps Surae ◽  
Spinal Reflex ◽  
Medial Gastrocnemius ◽  
Entire Group ◽  
Passive Components ◽  
Mechanical Coupling ◽  
Golgi Tendon Organs ◽  
Reflex Pathways ◽  
Tendon Organs ◽  
Triceps Surae Muscles

Receptor mechanisms underlying heterogenic reflexes among the triceps surae muscles of the cat. The soleus (S), medial gastrocnemius (MG), and lateral gastrocnemius (LG) muscles of the cat are interlinked by rapid spinal reflex pathways. In the decerebrate state, these heterogenic reflexes are either excitatory and length dependent or inhibitory and force dependent. Mechanographic analysis was used to obtain additional evidence that the muscle spindle primary ending and the Golgi tendon organ provide the major contributions to these reflexes, respectively. The tendons of the triceps surae muscles were separated and connected to independent force transducers and servo-controlled torque motors in unanesthetized, decerebrate cats. The muscles were activated as a group using crossed-extension reflexes. Electrical stimulation of the caudal cutaneous sural nerve was used to provide a particularly strong activation of MG and decouple the forces of the triceps surae muscles. During either form of activation, the muscles were stretched either individually or in various combinations to determine the strength and characteristics of autogenic and heterogenic feedback. The corresponding force responses, including both active and passive components, were measured during the changing background tension. During activation of the entire group, the excitatory, heterogenic feedback linking the three muscles was found to be strongest onto LG and weakest onto MG, in agreement with previous results concerning the strengths of heteronymous Ia excitatory postsynaptic potentials among the triceps surae muscles. The inhibition, which is known to affect only the soleus muscle, was dependent on active contractile force and was detected essentially as rapidly as length dependent excitation. The inhibition outlasted the excitation and was blocked by intravenous strychnine. These results indicate that the excitatory and inhibitory effects are dominated by feedback from primary spindle receptors and Golgi tendon organs. The interactions between these two feedback pathways potentially can influence both the mechanical coupling between ankle and knee.

Estrogen attenuates the cardiovascular and ventilatory responses to central command in cats

2002 ◽  
Vol 92 (4) ◽  
pp. 1635-1641 ◽  
Author(s):  
Shawn G. Hayes ◽  
Nicolas B. Moya Del Pino ◽  
Marc P. Kaufman
Keyword(s):  
Triceps Surae ◽  
Central Command ◽  
Neuronal Function ◽  
Ventilatory Responses ◽  
Exercise Pressor Reflex ◽  
Arterial Blood ◽  
Static Contraction ◽  
17Β Estradiol ◽  
Pressor Reflex ◽  
Triceps Surae Muscles

Static exercise is well known to increase heart rate, arterial blood pressure, and ventilation. These increases appear to be less in women than in men, a difference that has been attributed to an effect of estrogen on neuronal function. In decerebrate male cats, we examined the effect of estrogen (17β-estradiol; 0.001, 0.01, 0.1, and 1.0 μg/kg iv) on the cardiovascular and ventilatory responses to central command and the exercise pressor reflex, the two neural mechanisms responsible for evoking the autonomic and ventilatory responses to exercise. We found that 17β-estradiol, in each of the three doses tested, attenuated the pressor, cardioaccelerator, and phrenic nerve responses to electrical stimulation of the mesencephalic locomotor region (i.e., central command). In contrast, none of the doses of 17β-estradiol had any effect on the pressor, cardioaccelerator, and ventilatory responses to static contraction or stretch of the triceps surae muscles. We conclude that, in decerebrate male cats, estrogen injected intravenously attenuates cardiovascular and ventilatory responses to central command but has no effect on responses to the exercise pressor reflex.

Production of hydroxyl radicals in contracting skeletal muscle of cats

1996 ◽  
Vol 81 (3) ◽  
pp. 1197-1206 ◽  
Author(s):  
C. A. O'Neill ◽  
C. L. Stebbins ◽  
S. Bonigut ◽  
B. Halliwell ◽  
J. C. Longhurst
Keyword(s):  
Skeletal Muscle ◽  
Triceps Surae ◽  
Oxygen Species ◽  
Static Contraction ◽  
Maximal Tension ◽  
Cumulative Production ◽  
Triceps Surae Muscles ◽  
Specific Species

Reactive oxygen species increase during exhaustive contraction of skeletal muscle, but characterization of the specific species involved and their rates of production during nonexhaustive muscle contraction have not been investigated. We hypothesized that the production rate of hydroxyl radical (.OH) increases in contracting muscle and that this rate is attenuated by pretreatment with deferoxamine (Def) or dimethylthiourea (DMTU). We measured the rate of production of .OH before, during, and after 5 min of intermittent static contraction of the triceps surae muscles in cats (n = 6) using the formation of p-, m-, and o-tyrosines by hydroxylation of phenylalanine. L-Phenylalanine (30 mg/kg i.v.) was administered to each animal 3 min before contraction. Blood samples were collected from the popliteal vein 1 min before contraction; 1, 3, and 4.5 min during contraction; and 1 min after contraction. During and after contraction, the cumulative production rates of p-, m-, and o-tyrosines were elevated by 42.84 +/- 5.41, 0.25 +/- 0.04, and 0.21 +/- 0.03 nmol.min-1.g-1, respectively, compared with noncontracting triceps surae muscles. Pretreatment with Def (10 mg/kg i.v.; n = 5) or DMTU (10 mg/kg i.v.; n = 4) decreased the cumulative rates of production of p-, m-, and o-tyrosines during and after contraction. Additionally, the rate of tyrosine production increased in proportion to the percentage of maximal tension developed by the triceps surae muscles. These results directly demonstrate that .OH is produced in vivo in the skeletal muscle of cats during intermittent static contraction and that production can occur before the onset of fatigue.

Gadolinium attenuates exercise pressor reflex in cats

2001 ◽  
Vol 280 (5) ◽  
pp. H2153-H2161 ◽  
Author(s):  
Shawn G. Hayes ◽  
Marc P. Kaufman
Keyword(s):  
Pressor Response ◽  
Oxygen Demand ◽  
Muscle Afferents ◽  
Triceps Surae ◽  
Mechanical Stimuli ◽  
Group Iii ◽  
Exercise Pressor Reflex ◽  
Static Contraction ◽  
Pressor Reflex ◽  
Triceps Surae Muscles

The exercise pressor reflex, which arises from the contraction-induced stimulation of group III and IV muscle afferents, is widely believed to be evoked by metabolic stimuli signaling a mismatch between blood/oxygen demand and supply in the working muscles. Nevertheless, mechanical stimuli may also play a role in evoking the exercise pressor reflex. To determine this role, we examined the effect of gadolinium, which blocks mechanosensitive channels, on the exercise pressor reflex in both decerebrate and α-chloralose-anesthetized cats. We found that gadolinium (10 mM; 1 ml) injected into the femoral artery significantly attenuated the reflex pressor responses to static contraction of the triceps surae muscles and to stretch of the calcaneal (Achilles) tendon. In contrast, gadolinium had no effect on the reflex pressor response to femoral arterial injection of capsaicin (5 μg). In addition, gadolinium significantly attenuated the responses of group III muscle afferents, many of which are mechanically sensitive, to both static contraction and to tendon stretch. Gadolinium, however, had no effect on the responses of group IV muscle afferents, many of which are metabolically sensitive, to either static contraction or to capsaicin injection. We conclude that mechanical stimuli arising in contracting skeletal muscles contribute to the elicitation of the exercise pressor reflex.

Beta-contributions to fusimotor action in triceps surae muscles of decerebrated cats

1987 ◽  
Vol 57 (2) ◽  
pp. 574-595 ◽  
Author(s):  
S. E. Grill ◽  
W. Z. Rymer
Keyword(s):  
Muscle Force ◽  
Discharge Rate ◽  
Muscle Spindles ◽  
Triceps Surae ◽  
Medial Gastrocnemius ◽  
Gamma Activity ◽  
Response Patterns ◽  
Two Measures ◽  
Triceps Surae Muscles ◽  
Stimulation Of

The discharge of spindle afferents from medial gastrocnemius and soleus muscles was recorded in the decerebrated cat preparation, under isometric conditions and during ramp and hold stretches. Motor output was varied systematically by manual stimulation of the contralateral hindlimb. Twenty-six of 34 afferents showed response patterns consistent with enhancement of dynamic and/or static fusimotor input with increasing muscle force. To establish whether force-related fusimotor effects were mediated at least partly by beta-input, beta-innervation to these same spindles was sought, using a ventral root stimulation protocol. Twenty-three of the 34 afferents were shown to receive beta-innervation, which was most often static in type. For two measures of fusimotor action, the slope of the afferent dynamic rate-length relation and the discharge rate measured during the last portion of ramp stretch, significant increases in the measure, which paralleled increases in muscle force, made it statistically more likely that the afferent received beta-innervation. Our measures did not successfully predict the type of beta-input (beta-static or beta-dynamic). Procaine block of gamma-fibers produced substantial reductions in fusimotor effect in seven spindle afferents (although modest residual fusimotor effects were detectable for 3/7 afferents). The severity of these reductions indicates that beta-action probably requires concurrent gamma-input to the spindle in order to be effective. In support of this possibility, the fusimotor effects of electrical stimulation of single beta-fibers were greatly reduced for five out of six afferents during procaine block of gamma-fibers, compared with the beta-effects recorded when modest levels of spontaneous gamma-activity were present. We conclude that beta-innervation to muscle spindles of triceps surae is common and that this innervation exerts significant fusimotor effects. It appears likely that beta-motoneurons are able to produce both static and dynamic effects above extrafusal threshold, but that the actions require on-going gamma-activity in order to be effective.

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