The classification of afferents from muscle spindles of the jaw‐closing muscles of the cat.

Taylor, Anthony R.; Durbaba, Rade; Rodgers, J F

doi:10.1113/jphysiol.1992.sp019356

Cited by 44 publications

(73 citation statements)

References 33 publications

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“…It is noteworthy that it is the distributions of these two measures of the effect of SCh which become most markedly bimodal (APF being the sum of AIF and ADD is also bimodal). This appearance is much clearer in the distribution of the logarithmically Hald (1952) explained in the previous paper (Taylor et al 1992) and is applied to the data for ADD and CV in Fig. 5.…”

mentioning

confidence: 87%

“…The effects of SCh were therefore measured from the cycle histogram derived from cycles 5 to 9 after the i.v. injection rather than from cycles 10 to 14 as in the previous report for jaw muscles (Taylor et al 1992). one group of units shows virtually no change, while the rest show a wide range of increases.…”

mentioning

confidence: 95%

“…Originally the enhancement of dynamic sensitivity of primary afferents through contraction of bag1 (bl) fibres was the feature of chief interest (Rack & Westbury, 1966;Cody, Lee & Taylor, 1972) but later it was realized that the effect of contraction of bag2 (b2) fibres could also be estimated (Dutia, 1980;Price & Dutia, 1987;Price & Dutia, 1989). On this basis a detailed reexamination of jaw muscle spindle afferents has been carried out and reported in full in the preceding paper (Taylor, Durbaba & Rodgers, 1992). It was concluded that these spindle afferents could be classified into four subgroups according to the separate effects of SCh in increasing the dynamic response and the bias during repeated ramp and hold muscle stretches.…”

Section: Introductionmentioning

confidence: 99%

“…A tendency to bimodality of distribution is again obvious in all save ASI and ASD. As detailed in the previous paper (Taylor et al 1992) it is to be expected that SCh-induced contraction of b1 fibres will enhance dynamic stretch sensitivity which is best represented by ADD. The effect of b2 fibre contraction will be most marked on bias, which is measured by AIF (see Boyd, 1985).…”

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confidence: 99%

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The effect of succinylcholine on cat gastrocnemius muscle spindle afferents of different types.

Taylor¹,

Rodgers²,

Fowle³

et al. 1992

The Journal of Physiology

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SUMMARY1. A population of 269 gastrocnemius muscle spindle afferents have been studied in anaesthetized cats for the effects of succinylcholine (SCh) on their response to ramp and hold stretches repeated every 6 s. The effectiveness and reliability of the SCh test was improved by prior stimulation of the muscle at 10 Hz for 30 s to increase the blood flow.2. Responses have been assessed from averaged cycle histograms before and after a single iv. dose of SCh of 200 jag kg-'. As for previous studies of jaw muscle spindles the basic measurements were initial frequency (IF), peak frequency (PF) and static index (SI), the frequency 05 s after the end of the ramp of stretch. Dynamic difference (DD = PF-IF), dynamic index (DI = PF-SI) and static difference (SD = SI -IF) were derived from these and increases caused by SCh indicated by the prefix A. 3. ADD and AIF were each distributed bimodally and since they were uncorrelated formed the basis for a four-way classification. Since ADD can be attributed to activation of bag1 (b1) intrafusal fibres and AIF to bag2 (b2) fibres, while all afferents receive input from chain (c) fibres it is proposed as with the jaw spindles that the classes correspond to predominant influence from b1 c, b1 b2 c, b2 c and c intrafusal fibres.4. The proportion of units in the different groups were similar to those in the jaw muscles except for there being very few b1 c type in gastrocnemius. 5. Conduction velocity was bimodally distributed with the best dividing line at 63 2 m s51. The b1 b2c units were all, save one, in the fast group, while the b2 c units were equally divided between fast and slow.6. Mean control values for DD did not differ between the b1b2c and the b2c groups, which is taken to indicate that the b1 fibre does not contribute significantly to the dynamic stretch response of spindles with no intrafusal contraction.7. The results emphasize the importance of recognizing that some apparently primary afferents lack b, fibre influence, while many secondaries have marked b2fibre influence. 8. The importance of the SCh classification is discussed in relation to the identification of fusimotor effects on spindle discharge and in relation to studies of central connectivity.MS 9904

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confidence: 87%

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confidence: 95%

Section: Introductionmentioning

confidence: 99%

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confidence: 99%

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The effect of succinylcholine on cat gastrocnemius muscle spindle afferents of different types.

Taylor¹,

Rodgers²,

Fowle³

et al. 1992

The Journal of Physiology

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“…Peak frequency (PF) was the maximum at the end of the ramp of stretch and the static index (SI) the frequency 0 5 s later. From these were derived the dynamic difference (DD) as PF -IF, dynamic index (DI) as PF -SI and static difference (SD) as SI -IF (see Taylor, Durbaba & Rodgers, 1992a;Taylor et al 1992b). Where changes in these measures were produced by succinylcholine (Scoline, Duncan Flockhart & Co. Ltd, Greenford, England) or by fusimotor effects, the differences were symbolized by the prefix A, thus for example ADD means DD in the test condition minus the control value.…”

Section: Methodsmentioning

confidence: 99%

The use of sinusoidal and ramp stretch stimuli in characterizing fusimotor effects on cat muscle spindles

Rodgers¹,

Durbaba²,

Taylor³

et al. 1994

Experimental Physiology

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SUMMARYComparisons were made between the results of testing muscle spindle primary afferents with low-frequency, large-amplitude sine waves of muscle stretch and with repeating ramp-and-hold stretches. Three different situations were explored, namely, activation with succinylcholine (SCh), generation of various fusimotor outflow patterns by brainstem stimulation and fusimotor activation by stimulation of single ventral root y-axons. With ramp-and-hold stretches the effects of bag, fibre contraction were thought to be generally better represented by increases in the dynamic response to stretch (ADD) than by increases in dynamic index. The equivalent effect on the sine wave response was an increase in the magnitude of the fitted sine (AMag). Static effects were best measured by increases in the initial frequency for ramps (AIF) and by increases in the fitted centre frequency (ACF) for sines. There was good agreement between sine and ramp testing in the case of SCh effects, but much less consistency during brainstem stimulation. Sine wave testing can be regarded as less efficient than ramp testing in distinguishing between static and dynamic actions because dynamic fusimotor stimulation causes equal rises in CF and Mag, but fourfold larger rises in DD than in IF. Ramp responses with combined dynamic and static fusimotor stimulation showed increases of both IF and DD as expected, but whilst sine wave responses always showed increase in CF, they often showed no increase in Mag. Comparisons of the effects of SCh, central stimulation and fusimotor stimulation showed that it is important to recognize the different effects of chain and bag2 intrafusal fibre activation as components of static fusimotor excitation. Stimulation of driving static axons (chain activation) raised the IF and CF often with 1: 1 or 1:2 driving during the shortened phase of ramps and sines. However, the stretch response in both cases was either unchanged or reduced. Stimulation of a non-driving static fusimotor axon (bag2 activation) caused a marked rise in CF for sine waves and a fall in Mag, but a modest increase in ramp stretch sensitivity (DD) with no increase in dynamic index. A way is described for measuring flattening of sine wave responses as a possible way of detecting chain fibre activation. The consequences of these findings are discussed in relation to previous reports of the use of sine wave testing for assessing fusimotor mechanisms.

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Light microscopic observations of the contacts made between two spindle afferent types and ?-motoneurons in the cat trigeminal motor nucleus

et al. 1996

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Previous studies indicate that cat jaw-muscle spindle afferents can be divided into two types (type I and II) on the basis of their axonal trajectories. The present study examined the relationship between spindle afferent fibers and their target masseter alpha-motoneurons in the cat by using the intracellular horseradish peroxidase (HRP) injection technique, and provided several new findings on the synaptic organization generated between the two. Five type I afferent fiber-motoneuron pairs and nine type II afferent-motoneuron pairs were well stained with HRP. The following conclusions were drawn: 1) A motoneuron received contacts from only one collateral of any given spindle afferent. 2) The number of contacts made between an afferent and a motoneuron ranged from one to three. 3) The contacts made by a spindle afferent were on the same dendrite or dendrites branching from the same primary dendrite. 4) The vast majority of the contacts made by an afferent on a motoneuron were distributed in the dendritic tree within 600 microns from the soma, i.e., in the proximal three fourths of the dendritic tree. The differences observed between the two afferent types were as follows. First, type II afferent terminals made contacts on more distal dendrites of the motoneurons than did type I afferent terminals. Second, the contacts made between a type I afferent and a motoneuron were clustered together, but those made between a type II afferent and a motoneuron were widely dispersed. The present results provided the general rules of synaptic contacts between the spindle afferents and masseter alpha-motoneurons, and demonstrated that the spatial distribution of synaptic contacts on the dendritic tree was different between type I and type II afferents.

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The classification of afferents from muscle spindles of the jaw‐closing muscles of the cat.

Cited by 44 publications

References 33 publications

The effect of succinylcholine on cat gastrocnemius muscle spindle afferents of different types.

The effect of succinylcholine on cat gastrocnemius muscle spindle afferents of different types.

The use of sinusoidal and ramp stretch stimuli in characterizing fusimotor effects on cat muscle spindles

Light microscopic observations of the contacts made between two spindle afferent types and ?-motoneurons in the cat trigeminal motor nucleus

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