Intracellular autogenetic effects of muscular contraction on extensor motoneurones. The silent period

Granit, Raǵnar; Kellerth, Jan‐Olof; Szumski, Alfred J.

doi:10.1113/jphysiol.1966.sp007833

Cited by 51 publications

(15 citation statements)

References 30 publications

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“…Alternative reflex pathways which can be activated by a single afferent input have also been invoked to explain the spinal effects of DOPA (Dihydroxyphenylalanine; And6n, Jukes, Lundberg & Vyklicky, 1966). Thus, quite possibly the spindle group II afferents may produce different effects in different preparations and this would also be compatible with certain other findings in the anaesthetized cat (Bianconi, Granit & IReis, 1964;Granit, Kellerth & Szumski, 1966). At any rate, the previous experiments do not appear to conflict seriously with the present suggestion that the secondary endings of the muscle spindle are partly responsible for the tonic stretch reflex of the decerebrate cat.…”

Section: Discussionsupporting

confidence: 71%

Evidence that the secondary as well as the primary endings of the muscle spindles may be responsible for the tonic stretch reflex of the decerebrate cat

Matthews¹

1969

The Journal of Physiology

146

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SUMMARY1. The size of the tonic stretch reflex of the soleus or gastrocnemius muscle of the decerebrate cat has been compared with the size of the reflex contraction elicited in the same muscle by high-frequency vibration applied to its tendon.2. On the assumption that vibration preferentially excites the primary endings of the muscle spindles it may be used to estimate the relation between the reflex response and the frequency of the Ia input to the spinal cord. On this basis, the increase in tension evoked by increasing extension is too great to be explained by the increase in Ia input with extension previously found on single fibre recording in comparable preparations.3. When vibration was superimposed on stretch reflexes elicited by different extensions, the size of the additional contraction elicited by the vibration remained approximately constant. If the stretch and vibration reflexes both depended entirely upon the Ia pathway, then occlusion between them would have been expected instead of the simple summation which was found.4. The absence of occlusion was not due to variation of the contractile strength of the muscle with its extension. This was shown by finding that the reflex contraction of soleus produced by stimulating the medial gastrocnemius nerve also remained the same size when elicited at different lengths of the muscle.5. The reflex effects were studied of superimposing alternate stretches and releases of 0-2 mm, on extensions of several mm. The small stretches elicited responses which were larger than expected from the response to large stretches, and which were approximately the same size at different mean lengths of the muscle.6. It is concluded that the tonic stretch reflex of the decerebrate cat P. B. C. MATTHEWS cannot readily be explained solely by the increase in Ia discharge produced by stretching, as usually believed. Instead, it is suggested that the group II afferent fibres from the secondary endings of the muscle spindle also play an important part in its production.

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Section: Discussionsupporting

confidence: 71%

Evidence that the secondary as well as the primary endings of the muscle spindles may be responsible for the tonic stretch reflex of the decerebrate cat

Matthews¹

1969

The Journal of Physiology

146

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“…The electrically induced twitch provided an estimate of inhibitory reflex activity as well as aspects related to the muscle spindles. Muscle contraction produced by a maximal electrical stimulus of the motor nerve unloads the muscle spindles, causing a period of EMG silence during voluntary muscular activity (Merton, 1951;Granit et al, 1966;Higgins and Lieberman, 1968b). It has been pointed out that silence produced in this manner may also develop from synchronous refractoriness of motor neurones, Renshaw inhibition (antidromic), and post-synaptic inhibition related to the discharge of Golgi tendon afferent fibres (Matthews, 1964;Granit et al, 1966).…”

Section: Discussionmentioning

confidence: 99%

“…The silent period was obtained by an electrically induced contraction of a single muscle (adductor pollicis). During maximal stimulation the early portion of EMG silence was a manifestation of inhibitory actions, while events related to muscle spindle function were identifiable in the termination of the silence (Granit, Kellerth, and Szumski, 1966;Higgins and Lieberman, 1968a, b). METHOD The technique of obtaining the silent period of the adductor pollicis muscle has been described previously (Merton, 1951;Higgins and Lieberman, 1968a, b).…”

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confidence: 99%

Muscle silent period in Parkinson's disease

Higgins

Haidri

Wilbourn

1971

Journal of Neurology, Neurosurgery & Psychiatry

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SUMMARY The muscle silent period was measured in 11 patients with moderate to severe rigidity associated with Parkinson's disease. The determinations were made under conditions of maximum disability for each patient, since all medications had been withdrawn before testing. The duration of the EMG silence, produced by small and large electrical twitch contractions of the adductor pollicis muscle, fell within a range of values previously determined for normal individuals. Major alleviation of the rigidity and bradykinesia with chronic oral L-dopa therapy was not accompanied by any change in the silent period. It was concluded that in untreated Parkinsonism, and also after its treatment with L-dopa, the functioning of the muscle spindles and local inhibitory reflexes remains normal.Previous investigators (Angel, Hofmann, and Eppler, 1966), utilizing the unloading reflex, demonstrated that the electromyographic (EMG) silent periods in four patients with Parkinsonian rigidity were similar to those obtained in normal individuals. The present investigation, using 11 patients, demonstrated normal silent periods under conditions which provide additional insight into the reflex behaviour in Parkinsonism. The silent period was obtained by an electrically induced contraction of a single muscle (adductor pollicis). During maximal stimulation the early portion of EMG silence was a manifestation of inhibitory actions, while events related to muscle spindle function were identifiable in the termination of the silence (Granit, Kellerth, and Szumski, 1966; Higgins and Lieberman, 1968a, b). METHODThe technique of obtaining the silent period of the adductor pollicis muscle has been described previously (Merton, 1951; Higgins and Lieberman, 1968a, b). Two modifications were made to simplify the recording procedure.The first modification was that two skin surface electrodes with silver-silver chloride junctions (Beckman Bio-potential electrodes; diameter 2 mm) were used for EMG recording instead of needle electrodes. The active Identical silent periods were observed in the surface and needle electrode recordings obtained from a normal individual. The second modification was that stimulation of the ulnar nerve at the wrist and recording of EMG and tension responses were accomplished with a HewlettPackard Electromyograph (Model 1510A) equipped with a storage cathode ray tube and Polaroid camera.The ulnar nerve was stimulated at several intensities in order to compare the degree of inhibition associated with maximal and minimal isometric contractions. The stimuli occurred at equal or unequal intervals between I and 5 sec. Isometric tension was recorded with a Grass strain gauge (Model FT-10), as previously described. The amplified DC output of this gauge was applied directly to the vertical amplifier of the second recording channel of the electromyograph, by-passing the AC preamplifier.As in previous investigations of this type, close attention was given to the maintenance of steady tension and EMG levels before each electrical stimul...

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“…Secondly, the flexor muscle spindles were frequently found to fire bursts of activity during both the rising and the falling phase of the contraction. The late spindle burst is most probably caused by mechanical pull on the muscle spindles in relaxation and corresponds to the myotatic 'appendage' in extensors (Ballif, Fulton & Liddell, 1925;Granit et al 1966a). The spindle burst occurring during the rising phase of contractile tension is favoured by an increased muscle extension and is, at least to some extent, dependent upon activation of large fusimotor fibres (Figs.…”

Section: Discussionmentioning

confidence: 99%

Intracellular autogenetic and synergistic effects of muscular contraction on flexor motoneurones

Green¹,

Kellerth²

1967

The Journal of Physiology

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SUMMARY1. Intracellular records have been taken from cat motoneurones innervating flexor muscles of the hind limb. Contractions of the ankle flexors tibialis anterior and extensor digitorum longus were elicited by stimulation of the peripheral end of the cut L 7 ventral root and the reflex effects of these contractions were recorded in silent and repetitively firing motoneurones.2. Contraction usually produces a hyperpolarizing response inside flexor motoneurones. This hyperpolarization is tension-sensitive in the sense that when, at constant muscle extension, the strength of the contraction is increased, the magnitude of the inhibitory response is augmented.3. Increasing the resting length of the muscles, while using a stimulus of constant strength to the ventral root, causes this inhibitory response to increase in some cells. More often, however, the hyperpolarization caused by contraction is gradually reduced in duration and/or amplitude as the muscles are extended.4. Even with the muscles slackened, so that they develop no tension at their ends, contraction usually produces prominent hyperpolarization of the motoneurones.5. By passing polarizing currents or injecting chloride ions through the intracellular micro-electrode, the hyperpolarizing potentials produced by contraction of the slack and extended muscles are shown to be, at least in part, genuinely post-synaptic inhibitory events.6. When the neurone is fired repetitively by injected current, the 'silent period' in contraction corresponds to the hyperpolarization of the postsynaptic membrane. 10. A number of muscle spindles of the ankle flexors are activated by stimulation of the ventral root at a strength submaximal or just maximal for the a-motor fibres, despite the simultaneous unloading effect of the contracting extrafusal fibres. This spindle activation, which occurs mainly during the phase of tension development in contraction, is favoured by an increased extension of the muscle. Attempts were made to establish whether it is due to a-motor innervation of the receptors or to some mechanical interaction between the intra-and extrafusal muscle fibres.11. The possible central and peripheral causes of the changes in motoneurone excitability produced by flexor muscle contraction are discussed. It is suggested that tendon organs of flexor muscles strongly inhibit flexor motoneurones and that ac-motor innervation of muscle spindles is likely to play a more prominent role in flexors than in extensor muscles.

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Intracellular autogenetic effects of muscular contraction on extensor motoneurones. The silent period

Cited by 51 publications

References 30 publications

Evidence that the secondary as well as the primary endings of the muscle spindles may be responsible for the tonic stretch reflex of the decerebrate cat

Evidence that the secondary as well as the primary endings of the muscle spindles may be responsible for the tonic stretch reflex of the decerebrate cat

Muscle silent period in Parkinson's disease

Intracellular autogenetic and synergistic effects of muscular contraction on flexor motoneurones

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