Actions on gamma‐motoneurones elicited by electrical stimulation of group II muscle afferent fibres in the hind limb of the cat.

Appelberg, B; Hulliger, M.; Johansson, Håkan; Sojka, Peter

doi:10.1113/jphysiol.1983.sp014532

Cited by 64 publications

(47 citation statements)

References 20 publications

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“…According to results summarized by Appelberg (1981) and Appelberg et at. (1983b), group II afferents of the ipsilateral p.b.s.t.…”

Section: J Nothmentioning

confidence: 98%

Autogenetic inhibition of extensor gamma‐motoneurones revealed by electrical stimulation of group I fibres in the cat.

Noth¹

1983

The Journal of Physiology

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SUMMARY1. Forty functionally single y-efferents (20-42 m/s) to the triceps surae were isolated in ventral root filaments of the decerebrated and paralysed cat in order to study the effects of group I muscle afferents on their own fusimotor neurones. All the efferents studied were spontaneously active.2. During splitting the continuity of the efferent fibre was preserved so that the destination of the target muscle of the efferent could be determined by antidromic stimulation of the muscle nerve using the collision block technique. Thereafter the filament was cut so that the reflex response, uncontaminated by antidromic impulse invasion, could be recorded from the central end.3. Sixteen offorty y-efferents to the triceps were inhibited by repetitive stimulation (range -3 to -40 impulses/s) of the homonymous nerve within the group I range. Raising the stimulus strength above the group II threshold produced no further increase in inhibition. Twelve of these sixteen cells were also tested by stretching the triceps; ten showed marked inhibition, and two were not influenced.4. In ten of the sixteen inhibited cells, the autogenetic inhibition at maximum group I stimulus strength was larger than the maximum antidromic inhibition elicited by stimulation of the remainder of the cut ventral roots L7 and SI. Since both effects were additive, it is concluded that Renshaw inhibition is at least not solely responsible for the autogenetic inhibition.5. Consistent with this assumption is the observation that some cells receiving electrically evoked autogenetic inhibition were not susceptible to inhibition induced by small-amplitude vibration ofthe triceps. Since small-amplitude vibration is known to excite most ofthe I a afferents of the vibrated triceps, I b afferents must be involved in the autogenetic fusimotor inhibition.6. A contribution of I a afferents to the autogenetic inhibition (via a-motoneurones and Renshaw cells or via Ib inhibitory interneurones) seems likely since inhibition, induced by small-amplitude vibration, was detectable in many of the cells receiving autogenetic group I inhibition. All of these cells were susceptible to antidromic inhibition.* All the experimental work was carried out at

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“…According to results summarized by Appelberg (1981) and Appelberg et at. (1983b), group II afferents of the ipsilateral p.b.s.t.…”

Section: J Nothmentioning

confidence: 98%

Autogenetic inhibition of extensor gamma‐motoneurones revealed by electrical stimulation of group I fibres in the cat.

Noth¹

1983

The Journal of Physiology

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“…Renshaw cells affect all of these neurons (Hultborn et al, 1976). The group II interneurons which are located in the intermediate region and ventral horn (lamina VI-VIII) are considered to be the last order interneurons (Cavallari et al, 1987) and have strong excitatory effects on both α-and γ-motoneurons (Appelberg et al, 1983). The medullary inhibitory inputs to these lastorder interneurons, which are in parallel to both α-and γ-motoneurons (Takakusaki et al, 2001), may simultaneously alter the excitability of these neurons, and therefore play an important role in the regulation of postural muscle tone.…”

Section: (2) Reticulospinal Control Of Interneurons In Reflex Pathwaysmentioning

confidence: 99%

Medullary reticulospinal tract mediating a generalized motor inhibition in cats: iii. functional organization of spinal interneurons in the lower lumbar segments

2003

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“…Even the effects with the longest latencies occurred, at least with their principal components, well below the minimal group IV latency of the nerve from which they were elicited. The minimal group IV latencies for each nerve were calculated in the same way as the group III latencies (see Appelberg et al 1983b). Thus the latency values were derived using the mean values of the measured conduction distances, a maximum group IV conduction velocity of 2 m/sec (see e.g.…”

Section: Group III Action On Y-motoneuronesmentioning

confidence: 99%

Actions on gamma‐motoneurones elicited by electrical stimulation of group III muscle afferent fibres in the hind limb of the cat.

Appelberg¹,

Hulliger²,

Johansson³

et al. 1983

The Journal of Physiology

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172

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SUMMARY1. The reflex actions evoked by electrical stimulation of group III muscle afferent fibres were investigated with micro-electrode recordings from ninety-three ymotoneurones projecting to hind-limb muscles of cats anaesthetized with chloralose. For seventy-eight of the ninety-three y-cells the frequency of occurrence and types of effects mediated via group II and group III muscle fibres were compared.2. Seventy-seven of the cells tested at intensities which excited group III and seventy-five of the cells tested at intensities which excited both group II and group III afferent fibres were classified as either static or dynamic, using the method of mesencephalic stimulation (Appelberg, 1981).3. The responsiveness of the whole sample of y-motoneurones to inputs from group III muscle fibres was high and comparable to that found with group II fibres.4. It was found that group III muscle fibres acted preferentially on static y-motoneurones. In contrast, group II fibres acted preferentially on dynamic y-motoneurones.5. Both excitatory and inhibitory effects were provoked by stimulation of group III fibres. Generally excitation was more frequent than inhibition.6. A strong dominance of excitation over inhibition was found in flexor muscles, and a weaker prevalence of excitation was also encountered in extensor muscles. This prevalence of excitation in extensor y-motoneurones is in contrast to the striking predominance ofgroup III-evoked inhibition ofextensor a-motoneurones as described by the flexion reflex afferents concept. 7. A comparative survey is also given of the patterns of responses elicited in individual posterior biceps-semitendinosus and gastrocnemius-soleus y-cells by stimulation of group II and group III fibres. These data further corroborate the view that reflexes from high-threshold muscle afferent fibres to y-motoneurones are organized differently from those to a-motoneurones.8. The functional implications of these findings are discussed. It is proposed that the pools of y-motoneurones should be considered as integrative systems intercalated

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Actions on gamma‐motoneurones elicited by electrical stimulation of group II muscle afferent fibres in the hind limb of the cat.

Cited by 64 publications

References 20 publications

Autogenetic inhibition of extensor gamma‐motoneurones revealed by electrical stimulation of group I fibres in the cat.

Autogenetic inhibition of extensor gamma‐motoneurones revealed by electrical stimulation of group I fibres in the cat.

Medullary reticulospinal tract mediating a generalized motor inhibition in cats: iii. functional organization of spinal interneurons in the lower lumbar segments

Actions on gamma‐motoneurones elicited by electrical stimulation of group III muscle afferent fibres in the hind limb of the cat.

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