Organization of motor units following cross‐reinnervation of antagonistic muscles in the cat hind limb.

Gordon, Tessa; Stein, Richard B.; Thomas, C. K.

doi:10.1113/jphysiol.1986.sp016090

Cited by 23 publications

(12 citation statements)

References 15 publications

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“…Full recovery of motoneuron properties and synaptic contacts onto axotomised motoneurons occurs following muscle innervation.33 When motoneurons reinnervate their former or antagonistic muscles, the physiological relationships between nerve and muscle properties also retumed to normal. Th-us, the tension and contractile speed of the muscle units were directly related to the amplitude of the extracellularly recorded action potential, as found in normally innervated muscles.12 34 Self-reinnervated muscles function appropriately during locomotion. In comparison, cross-reinnervated cat muscles typically fired according to the pattern expected of the innervating motor pool during locomotion.35-3 Therefore, these data would tend to suggest that even though nerve and muscle unit properties are reestablished after nerve section and resuture, the motor units are recruited at a level of force that is appropriate within their original motor pool as is proposed here.…”

Section: Innervation Of Reinnervated Musclesmentioning

confidence: 88%

Patterns of reinnervation and motor unit recruitment in human hand muscles after complete ulnar and median nerve section and resuture.

Thomas¹,

Stein²,

Gordon³

et al. 1987

Journal of Neurology, Neurosurgery & Psychiatry

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If we want to tie a shoelace, write a letter, eat, or play a musical instrument, we are confronted with the need to control our hand muscles precisely. Our ability to co-ordinate these and many other fine movements is generally assumed to result from direct corticospinal connections to the motoneurons innervating the hand muscles' 2 and from an orderly recruitment of motoneurons from small to large within each spinal motor pool.34One notable exception to this recruitment pattern occurred after resuture of a completely severed ulnar nerve in the forearm. Normal motor unit twitch amplitudes were re-established but the threshold force for recruitment of these reinnervated motor units remained abnormal. In addition to a disordered recruitment of motor units, these individuals showed poor motor co-ordination for fine movements.5 In these patients, the axons had been severed and so disconnected from a pathway to their peripheral end organs. As the ulnar nerve contains axons which innervate several intrinsic hand muscles, many muscles were denervated. During regeneration, the axons had to grow across the suture line and along the endoneurial tubes to innervate the denervated muscle fibres

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Section: Innervation Of Reinnervated Musclesmentioning

confidence: 88%

Patterns of reinnervation and motor unit recruitment in human hand muscles after complete ulnar and median nerve section and resuture.

Thomas¹,

Stein²,

Gordon³

et al. 1987

Journal of Neurology, Neurosurgery & Psychiatry

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“…Specificity of reinnervation in whole muscles may better be characterized by description of their motor unit population (Burke, Levine, Tsairis & Zajac, 1973;Kugelberg, 1973;Gordon & Stein, 1982a;Gordon, Stein & Thomas, 1986). At the single motor unit level, proportions of fast and slow motor unit types in reinnervated cat muscles after resuture of a single muscle nerve were normal (Gordon & Stein, 1982a).…”

Section: Introductionmentioning

confidence: 99%

Reinnervation of the lateral gastrocnemius and soleus muscles in the rat by their common nerve.

Gillespie¹,

Gordon²,

Murphy³

1986

The Journal of Physiology

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SUMMARY1. To determine whether there is any specificity of regenerating nerves for their original muscles, the common lateral gastrocnemius soleus nerve (l.g.s.) innervating the fast-twitch lateral gastrocnemius (l.g.) and slow-twitch soleus muscles was sectioned in the hind limb of twenty adult rats. The proximal nerve stump was sutured to the dorsal surface of the l.g. muscle and 4-14 months later, the contractile properties of the reinnervated l.g. and soleus muscles and their single motor units were studied by dissection and stimulation of the ventral root filaments. Contractile properties of normal contralateral muscles were examined for comparison and motor units were isolated in l.g. and soleus muscles for study in a group of untreated animals.2. Measurement of time and rate parameters of maximal twitch and tetanic contractions showed that the rate of development of force increased significantly in reinnervated soleus muscles and approached the speed of l.g. muscles but rate of relaxation did not change appreciably. In reinnervated l.g. muscles, contraction speed was similar to normal l.g. muscles but relaxation rate declined toward the rates of relaxation in control soleus muscles.3. After reinnervation by the common l.g.s. nerve, the proportion of slow motor units in l.g. increased from 10 to 31 % and decreased in soleus from 80 to 31 %. The relative proportions of fast and slow motor units in each muscle were the same as the proportions of fast and slow units in the normal l.g. and soleus muscles combined. 4. It was concluded that fast and slow muscles do not show any preference for their former nerves and that the change in the force profile of the reinnervated muscles is indicative of the relative proportions of fast and slow motor units: fast units dominate the contraction phase and slow units the relaxation phase of twitch and tetanic contractions of the muscle.

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“…Briefly, the MG muscle and its innervation were surgically isolated for EMG and force recordings in response to stimulation of single axons or the MG nerve. Evoked action potentials of single MG motor nerves were recorded extracellularly using a triphasic electrode configuration in which EMG pickup was minimized (Gordon et al 1986). The distal tendon of the MG muscle was fastened to a force transducer for recording isometric whole muscle (Grass FT 10) and motor unit force (Kulite transducer).…”

Section: Methodsmentioning

confidence: 99%

“…Developmentally, the regulation of muscle fibre contractile and metabolic properties has generally been attributed to some property of the innervating motoneurone (Vrbova et al 1995). However, following axonal regeneration, several studies at the single motor unit level have indicated that neural conversion of reinnervated muscle fibres properties is incomplete (Dum, O'Donovan, Toop, Tsairis, Pinter & Burke, 1985; Gordon, Stein & Thomas, 1986; Foehring, Sypert & Munson, 1986 b ; Gillespie, Gordon & Murphy, 1987; Gordon, Thomas, Stein & Erdebil, 1988; Cope, Webb & Botterman, 1991; Unguez, Roy, Pierotti, Bodine‐Fowler & Edgerton, 1995). The factors limiting complete neural conversion of muscle fibre properties following regeneration in the adult are not known.…”

mentioning

confidence: 99%

Incomplete rematching of nerve and muscle properties in motor units after extensive nerve injuries in cat hindlimb muscle

Rafuse

Gordon

1998

The Journal of Physiology

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Motor units were characterized in partially denervated or completely denervated and reinnervated cat medial gastrocnemius (MG) muscles where the number of innervating motor axons was severely reduced to determine (1) to what extent the nerve and muscle properties are rematched in enlarged motor units, (2) whether the normal size relationships between axon size, unit tetanic force and contractile speed are re‐established, and (3) whether the type of nerve injury and/or repair affects the re‐establishment of nerve and muscle properties. Single MG units were sampled in (1) partially denervated muscles and in reinnervated muscles after either (2) crushing or (3) transecting the nerve and suturing its proximal end to either the distal nerve stump (N‐N), or (4) directly to the muscle fascia (N‐M). The majority (75‐88 %) of motor units in all muscles were classified as S (slow), FR (fast fatigue resistant), FI (fast fatigue intermediate) and FF (fast fatigable). However, there was an increased number of FI and unclassifiable motor units compared to normal. These results suggest that motor unit properties are not entirely regulated by the reinnervating motoneurone. Despite more overlap in the range of unit force between different motor unit types the tetanic force of each type increased in all muscles when reinnervated by few (< 50 %) motor axons. This increase in unit force was due to an expansion in motor unit innervation ratio. The normal relationships between axon size, unit tetanic force, and contractile speed were re‐established in all muscles except when reinnervated by < 50 % of their normal complement of motor units after N‐M suture. This lack of correlation was due to the reduced fast glycolytic (FG) fibre size and the proportionately greater increase in force of the S units. After reinnervation the ranges in fibre cross‐sectional area within single FF units were very similar to those found within the entire FG fibre population. These results show that when few axons make functional connections in partially denervated or reinnervated muscles the normal relationships between axon size and motor unit contractile properties are re‐established provided the nerves regenerate within the distal nerve sheath. This rematching of motoneurone size and motor unit contractile properties occurs primarily because the size of the motor axon governs the number of muscle fibres it supplies.

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Organization of motor units following cross‐reinnervation of antagonistic muscles in the cat hind limb.

Cited by 23 publications

References 15 publications

Patterns of reinnervation and motor unit recruitment in human hand muscles after complete ulnar and median nerve section and resuture.

Patterns of reinnervation and motor unit recruitment in human hand muscles after complete ulnar and median nerve section and resuture.

Reinnervation of the lateral gastrocnemius and soleus muscles in the rat by their common nerve.

Incomplete rematching of nerve and muscle properties in motor units after extensive nerve injuries in cat hindlimb muscle

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