Reflex effects on γ fusimotor neurones of chemically induced discharges in small-diameter muscle afferents in decerebrate cats

Jovanovic, Ksenija; Anastasijević, Radmila; Vucˇo, Jovan

doi:10.1016/0006-8993(90)91528-o

Cited by 67 publications

(26 citation statements)

References 23 publications

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“…However, other factors could counteract such effects. In the cat, group III and IV muscle afferents can increase fusimotor discharge (Jovanovic et al, 1990) and hence spindle discharge during muscle fatigue (Ljubisavljevic et al, 1992). Second, group III and IV afferents may alter recurrent inhibition.…”

Section: Discussionmentioning

confidence: 99%

Fatigue-Sensitive Afferents Inhibit Extensor but Not Flexor Motoneurons in Humans

Martin¹,

Smith²,

Butler³

et al. 2006

J. Neurosci.

161

159

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The role of group III and IV muscle afferents in controlling the output from human muscles is poorly understood. We investigated the effects of these afferents from homonymous or antagonist muscles on motoneuron pools innervating extensor and flexor muscles of the elbow. In study 1, subjects (n ϭ 8) performed brief maximal voluntary contractions (MVCs) of elbow extensors before and after a 2 min MVC of the extensors. During MVCs, electromyographic responses from triceps were evoked by stimulation of the corticospinal tracts [cervicomedullary motor evoked potentials (CMEPs)]. The same subjects repeated the protocol, but input from fatigue-sensitive afferents was prolonged after the fatiguing contraction by maintained muscle ischemia. In study 2, CMEPs were evoked in triceps during brief extensor MVCs before and after a 2 min sustained flexor MVC (n ϭ 7) or in biceps during brief flexor MVCs before and after a sustained extensor MVC (n ϭ 7). Again, ischemia was maintained after the sustained contractions. During sustained MVCs of the extensors, CMEPs in triceps decreased by ϳ35%. Without muscle ischemia, CMEPs recovered within 15 s, but with maintained ischemia, they remained depressed (by ϳ28%; p Ͻ 0.001). CMEPs in triceps were also depressed (by ϳ20%; p Ͻ 0.001) after fatiguing flexor contractions, whereas CMEPs in biceps were facilitated (by ϳ25%; p Ͻ 0.001) after fatiguing extensor contractions. During fatigue, inputs from group III and IV muscle afferents from homonymous or antagonist muscles depress extensor motoneurons but facilitate flexor motoneurons. The more pronounced inhibitory influence of these afferents on extensors suggests that these muscles may require greater cortical drive to generate force during fatigue.

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Section: Discussionmentioning

confidence: 99%

Fatigue-Sensitive Afferents Inhibit Extensor but Not Flexor Motoneurons in Humans

Martin¹,

Smith²,

Butler³

et al. 2006

J. Neurosci.

161

159

View full text Add to dashboard Cite

show abstract

“…4). Referring to the previous presentation of an opposite mechanism, the ''vicious circle'' hypothesis is based on several works in which increased fusimotor activity was observed after intraarterial injection of pro-inflammatory substances (Jovanovic´et al 1990). It has also been suggested that increased fusimotor activity evoked by nociceptive afferents of a given muscle might lead to increased activation of muscle spindle afferents (Djupsjo¨backa et al 1995).…”

Section: Delayed Fatigue Effectsmentioning

confidence: 98%

Effects of long- and short-term fatiguing stretch-shortening cycle exercises on reflex EMG and force of the tendon-muscle complex

Nicol

Kuitunen

Kyröläinen

et al. 2003

European Journal of Applied Physiology

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This study examined the fatigue effects of stretch-shortening cycle exercises of different intensity and duration on stretch reflex EMG and mechanical responses of the triceps surae muscle. Twelve subjects performed either a 10-km run ( n=6) or short but exhaustive rebound exercise on a sledge apparatus ( n=6). Passive reflex tests (mechanically induced ankle dorsiflexions) were examined before, after as well as 2 h, 2 and 7 days after exercise. Mechanical reflex responses were recorded from the ergometer torque signal. An acute contractile failure was observed as large reductions in twitch responses, especially in the sledge subgroup who showed high post-exercise peak blood lactate and an increased EMG/torque ratio. Independently of the exercise, the delayed fatigue analysis revealed strong relationships between the reflex-induced EMG and mechanical changes. In addition to muscle damage, these results may be explained by inhibitory effects via the sensitisation of small muscle afferents particularly during the exercise-induced delayed recovery process.

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“…Nevertheless, observations that algesic chemical stimulation produces both excitatory and inhibitory responses in fusimotor neurons and spindle afferents complicate predictions that accumulation of metabolites invariably leads to increased spindle sensitivity. Stimulation of group III muscle afferents, has been shown to produce either an activation or inhibition of static gamma-motoneurons [18,19] in limb muscles. This also seems to be the case for jaw muscles.…”

Section: Discussionmentioning

confidence: 99%

The influence of pain on masseter spindle afferent discharge

Capra¹,

Hisley²,

Masri³

2007

Archives of Oral Biology

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SummaryMuscle spindles provide proprioceptive feedback supporting normal patterns of motor activity and kinesthetic sensibility. During mastication, jaw muscle spindles play an important role in monitoring and regulating the chewing cycle and the bite forces generated during mastication. Both acute and chronic orofacial pain disorders are associated with changes in proprioceptive feedback and motor function. Experimental jaw muscle pain also alters the normal response of masseter spindle afferents to ramp and hold jaw movements [1]. It has been proposed that altered motor function and proprioceptive input results from group III muscle afferent modulation of the fusimotor system which alters spindle afferent sensitivity in limb muscles [2]. The response to nociceptive stimuli may enhance or reduce the response of spindle afferents to proprioceptive stimuli. Several experimental observations suggesting the possibility that a similar mechanism also functions in jaw muscles are presented in this report. First, evidence is provided to show that nociceptive stimulation of the masseter muscle primarily influences the amplitude sensitivity of spindle afferents with relatively little effect on the dynamic sensitivity [3]. Second, reversible inactivation of the caudal trigeminal nuclei attenuates the nociceptive modulation of spindle afferents. Finally, functionally identified gamma-motoneurons in the trigeminal motor nucleus are modulated by intramuscular injection with algesic substances. Taken together, these results suggest that pain-induced modulation of spindle afferent responses are mediated by small diameter muscle afferents and that this modulation is dependent, in part, on the relay of muscle nociceptive information from trigeminal subnucleus caudalis onto trigeminal gamma-motoneurons. The implication of these results will be considered in light of current theories on the relationship between jaw muscle pain and oral motor function.

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Reflex effects on γ fusimotor neurones of chemically induced discharges in small-diameter muscle afferents in decerebrate cats

Cited by 67 publications

References 23 publications

Fatigue-Sensitive Afferents Inhibit Extensor but Not Flexor Motoneurons in Humans

Fatigue-Sensitive Afferents Inhibit Extensor but Not Flexor Motoneurons in Humans

Effects of long- and short-term fatiguing stretch-shortening cycle exercises on reflex EMG and force of the tendon-muscle complex

The influence of pain on masseter spindle afferent discharge

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