Recurrent actions on gamma‐motoneurones mediated via large and small ventral root fibres in the cat.

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

doi:10.1113/jphysiol.1983.sp014534

Cited by 34 publications

(15 citation statements)

References 28 publications

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“…For g.s., the dynamic cells were twice as frequent as static cells. This is in contrast to previous studies in which static fibres prevailed over dynamic fibres by a factor of two to three, when they were classified directly on the basis of their action on spindle afferent units (Matthews, 1972 Since recurrent effects from y-axon collaterals to y-cells have been described (Appelberg, Hulliger, Johansson & Sojka, 1983c) For all input nerves, the shortest pathways for inhibitory effects were one or two synapses longer than the fastest excitatory pathways.…”

Section: Discussioncontrasting

confidence: 60%

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

Appelberg¹,

Hulliger²,

Johansson³

et al. 1983

The Journal of Physiology

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SUMMARY1. The reflex effects elicited by electrical stimulation of group II muscle afferent fibres were recorded with micro-electrodes in ninety-eight hind-limb y-motoneurones of cats anaesthetized with chloralose.2. Eighty-one of the y-cells were classified as either static or dynamic by means of stimulation in the mesencephalic area for dynamic control known to influence dynamic y-motoneurones selectively.3. A high responsiveness to activity in group II muscle fibres was found for the whole sample of y-cells.4. Group II muscle action on dynamic y-motoneurones was found to be more frequent than that on static ones.5. Excitation from group II fibres outweighed inhibition. This was clear cut for flexor y-motoneurones. In extensor y-cells, excitation prevailed by a small margin only. However, for both static and dynamic extensor y-cells, excitation prevailed from both posterior biceps-semitendinosus and the gastrocnemius-soleus nerves, whereas inhibition was more frequent from the deep peroneal and quadriceps nerves.6. All the reflex effects studied were likely to be mediated via oligosynaptic pathways. The shortest latencies of excitatory effects were compatible with a disynaptic coupling. The fastest inhibitions were presumably trisynaptic.7. The present findings, supported by a parallel study of reflexes evoked by group III muscle afferents, strongly suggest that the reflexes on y-motoneurones are not organized in accordance with the concept of flexion reflex afferents as conceived for a-motoneurones.8. The interpretation of the results suggests a particularly independent position for dynamic y-cells in relation to a-and static y-motoneurones. Hence, the results also furnish an argument against the concept of a-y linkage.

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Section: Discussioncontrasting

confidence: 60%

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

Appelberg¹,

Hulliger²,

Johansson³

et al. 1983

The Journal of Physiology

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“…A short time ago Appelberg et al (1982Appelberg et al ( , 1983a showed, in a series of experiments made with intra-and extracellular recordings from a large sample of lumbar y-motoneurones, that segmental reflexes from muscle afferents to ymotoneurones differ appreciably from those to y-motoneurones. They suggested that the intricacy and variability of the reflex pattern found from high threshold muscle afferents on y-cells is incompatible with a strict parallelism between a-and y-activity during active movements.…”

Section: Discussionmentioning

confidence: 99%

“…The study was carried out on the same sample of classified y-cells (dynamic and static) for which the effects elicited from muscle afferent fibres, from recurrent motor-axon collaterals and from the rubrospinal and rubro-bulbospinal tracts, have already been reported on (Appelberg, Hulliger, Johansson & Sojka, 1982, 1983a.…”

Section: Introductionmentioning

confidence: 99%

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

Johansson¹,

Sojka²

1985

The Journal of Physiology

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132

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SUMMARY1. The reflex actions elicited by graded electrical stimulation ofhind-limb cutaneous (sural, superficial peroneal and tibial) nerves were investigated with intra-and extracellular micro-electrode recordings in y-motoneurones projecting to hind-limb muscles in twenty-four cats anaesthetized with a-chloralose.2. In total, reflex responses of 100 y-motoneurones were analysed. 82 of the y-cells were classified as dynamic (43) or static (39) using the method of mesencephalic stimulation (Appelberg, Hulliger, Johansson & Sojka, 1982).3. The general responsiveness (i.e. number of input nerves with effect/number of input nerves tested) of the whole sample of y-cells to stimulation of skin nerves was extremely high (94-8 00). All negative observations were encountered among static and non-classified y-cells.4. Generally, the stimulation strengths needed for evoking effects in the y-cells were very low. A majority of the excitatory effects in the dynamic cells appeared with stimulation intensities below 1.5 threshold (T), while most static cells were excited with stimulation strengths between 1.5 and 2 T. Also a statistical comparison of the populations of stimulation strength thresholds for the excitatory effects revealed a significant difference (P < 0 0009) between dynamic and static y-cells. By contrast, the thresholds for inhibitory effects in dynamic cells were slightly higher than for excitatory effects (P < 0 0009). As regards excitation of static cells, inhibition of dynamic cells and inhibition of static cells, no statistically significant threshold differences were found. 5. A strong dominance of excitation over inhibition was found in both dynamic and static flexor (posterior biceps and semitendinosus) y-motoneurones from all input nerves.6. In comparison to flexor y-motoneurones, there was a much higher incidence of inhibitory and mixed (excitatory and inhibitory) responses in extensor (triceps) y-motoneurones, from all nerves tested. For dynamic cells there was an about even balance between excitation and inhibition, while for static cells inhibition seemed to prevail.7. The latencies for excitatory effects in dynamic y-cells differed from those in static y-cells (P < 0-027). The shortest latencies of excitatory effects found for dynamic y-cells indicate a disynaptic coupling, while for static cells the shortest route H. JOHANSSON AND P. SOJKA seemed to involve at least three synapses. Inhibitory effects on both static and dynamic y-cells were generally found to be polysynaptically mediated, but a single case of evidence for trisynaptically coupled inhibition was observed for a dynamic gastrocnemius et soleus y-cell.8. The general differences between the subpopulations of y-motoneurones were found to mask a remarkable amount of variation among the individual y-cells, as regards thresholds, latencies and types of effects from the different skin nerves.9. A comparative survey is given where the effects on y-motoneurones are discussed in relation to the known effects on a-motoneurones. It is concluded t...

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“…~-Onto-7 recurrent inhibition has now been unequivocally demonstrated (Brown et al 1968a,b;Ellaway 1968Ellaway , 1971Grillner 1969a;Noth 1971;Fromrn et al 1974;Frornm and Noth 1976;Ellaway and Murphy 1981;Appelberg et al 1983d). Yet from all these studies it became quite evident that recurrent inhibition of 7-motoneurones is less frequent and less sizable than that of ~-motoneurones.…”

Section: ~-Onto-a Renshaw Inhibition Is Widespread and Powerful It Imentioning

confidence: 99%

“…The relative scarcity of recurrent inhibition in 7-motoneurones therefore indicates that Renshaw cell output is preferentially directed towards a-motoneurones. Nevertheless, when it occurs, recurrent inhibition of v-cells may also be elicited from other than homonymous sources (Ellaway 1971(Ellaway , 1976Appelberg et al 1983d) but not from antagonist muscle nerves (Noth 1971, Appelberg et al 1983d.…”

Section: ~-Onto-a Renshaw Inhibition Is Widespread and Powerful It Imentioning

confidence: 99%

The mammalian muscle spindle and its central control

Hulliger

1984

Reviews of Physiology, Biochemistry and Pharmacology

242

156

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Recurrent actions on gamma‐motoneurones mediated via large and small ventral root fibres in the cat.

Cited by 34 publications

References 28 publications

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

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

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

The mammalian muscle spindle and its central control

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