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B Appelberg

Publications and source records attributed to B Appelberg.

35 records · Page 2Linked to original sources
PubMed1983

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

The reflex actions evoked by electrical stimulation of group III muscle afferent fibres were investigated with micro-electrode recordings from ninety-three gamma-motoneurones projecting to hind-limb muscles of cats anaesthetized with chloralose. For seventy-eight of the ninety-three gamma-cells the frequency of occurrence and types of effects mediated via group II and group III muscle fibres were compared. 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). The responsiveness of the whole sample of gamma-motoneurones to inputs from group III muscle fibres was high and comparable to that found with group II fibres. It was found that group III muscle fibres acted preferentially on static gamma-motoneurones. In contrast, group II fibres acted preferentially on dynamic gamma-motoneurones. Both excitatory and inhibitory effects were provoked by stimulation of group III fibres. Generally excitation was more frequent than inhibition. 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 gamma-motoneurones is in contrast to the striking predominance of group III-evoked inhibition of extensor alpha-motoneurones as described by the flexion reflex afferents concept. A comparative survey is also given of the patterns of responses elicited in individual posterior biceps-semitendinosus and gastrocnemius-soleus gamma-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 gamma-motoneurones are organized differently from those to alpha-motoneurones. The functional implications of these findings are discussed. It is proposed that the pools of gamma-motoneurones should be considered as integrative systems intercalated between descending and reflex pathways on the one hand and the skeletomotor neurones on the other. The descending messages and the multisensory peripheral information, integrated in the fusimotor neurones, undergo final adjustment in the muscle spindle. The link to the skeletomotor neurones is formed by the primary spindle afferents. These constitute a final common input, conveying integrated detailed polymodal feed-back, to the central nervous system. This new concept is referred to as the 'final common input' hypothesis.

Action Potentials↗
PubMed1983

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

Effects on single lumbar gamma-motoneurones, mediated via fibres running in the ventral roots, were studied by micro-electrode recording in cats anaesthetized with chloralose. Graded electrical stimulation of ventral roots or of peripheral nerves was used. The cells were identified as gamma-motoneurones by antidromic stimulation and by measurement of their axonal conduction velocity. Some of the cells were classified as static or dynamic. The findings confirm the previously demonstrated existence of low-threshold, presumed recurrent, inhibition of both static and dynamic gamma-motoneurones. Strong evidence for the occurrence of high-threshold recurrent inhibition of gamma-motoneurones is also presented. In addition, excitatory effects on gamma-cells, also mediated via fibres in the ventral roots, are described. The low-threshold effects from ventral root fibres are attributed to recurrent alpha-collateral activity and the high-threshold effects to gamma-collateral activity. The significance of recurrent inhibition of gamma-motoneurones is discussed in relation to the 'gain regulator' concept proposed by Hultborn, Lindström & Wigström (1979).

Action Potentials↗
PubMed1982

An intracellular study of rubrospinal and rubro-bulbospinal control of lumbar gamma-motoneurones.

The actions elicited by electrical stimulation of the rubrospinal path in NR (nucleus ruber), and by stimulation of the rubro-bulbospinal path in MesADC (mesencephalic area for dynamic control), were studied with intra-, juxta- or extracellular recordings in lumbar gamma-motoneurones of cats anaesthetized with chloralose. The results were obtained during a series of experiments in which reflex effects from muscle, skin and joint afferents were also investigated. 90 cells tested with stimulation both in NR and in MesADC were classified (cf. Appelberg 1981) as dynamic (influenced from MesADC) or static (not influenced). 84 of these gamma-cells responded to stimulation in the red nucleus. The same response pattern was found for dynamic and static gamma-cells. For flexor cells, excitation was by far predominant while equal numbers of extensor cells showed excitatory and inhibitory effects. The shortest route to both static and dynamic gamma-cells was disynaptic. With stimulation of the rubro-bulbospinal path, excitatory effects were more than twice as frequent as inhibitory effects. No clearcut difference was seen between extensor and flexor cells. The segmental latency for rubro-bulbospinally mediated excitatory effects could be measured for only one cell, and it is tentatively suggested that the pathway to this dynamic gamma-motoneurone involves one or two interneurones more than in the rubrospinal pathway. Spontaneous activity was significantly more common among the dynamic cells, but the axonal conduction velocities of dynamic and static cells did not differ. The similarities between rubro-spinal effects on alpha-motoneurones and both classes of gamma-motoneurones indicate that the rubrospinal tract has the ability to coactivate alpha- and gamma-motoneurones (Granit 1955, 1979). The comparison of the properties of the population of gamma-cells classified as dynamic or static showed marked differences strengthening the reliability of the previously introduced classification method.

Afferent Pathways↗
PubMed1982

Fusimotor reflexes in triceps surae elicited by natural stimulation of muscle afferents from the cat ipsilateral hind limb.

1. Experiments were performed in forty-one cats anaesthetized with chloralose.2. The aim of the study was to investigate whether activity in stretch-sensitive muscle receptors may cause reflex effects in fusimotor neurones.3. Activity in fusimotor neurones was studied indirectly by recording from primary and secondary muscle spindle afferents of the triceps surae muscle. The mean rate of firing of the afferents as well as either dynamic index (during ramp extension) or modulation (during sinusoidal extension) was determined. This was done under control conditions, with the posterior biceps-semitendinosus muscles relaxed, and under test conditions, with the same muscles extended.4. All together, seventy-one primary afferents were studied quantitatively. Pure or predominantly dynamic effects were observed in twenty-two, pure or predominantly static effects in nine and no statistically significant effects in forty of the units. Amongst seven secondary afferents studied, two showed weak fusimotor activation, the other five were not influenced.5. Electrical stimulation of the posterior biceps-semitendinosus or medial gastrocnemius nerves at group II strength was observed to cause dynamic fusimotor reflexes on a number of occasions.6. The reflex effects observed were, on many occasions, recorded in spinalized preparations.7. The reflex effects were not accompanied by any detectable e.m.g. activity in triceps, as judged from surface e.m.g. recordings. The reflex effects observed are therefore tentatively ascribed to activation of gamma-motoneurones, yet a contribution from beta-motoneurones cannot wholly be excluded.8. On the basis of available evidence concerning reflex connexions to gamma-motoneurones from various muscle afferents, it is suggested that the effects observed were caused by activation of muscle spindle secondary endings.

Animals↗
PubMed1975

Rubrospinal control of static and dynamic fusimotor neurones.

Rubrospinal effects on about 60 extracellularyl recorded gamma-motoneurones were studied in anesthetized cats. All cells were antidromically identified from various muscle nerves. 23 cells were regarded as dynamic as they were activated from a mesencephalic region previously known to influence selectively muscle spindle dynamic sensitivity. The pattern of rubrospinal influence on static fusimotor neurones to different muscles closely followed that previously demonstrated for alpha-motoneurones with pr edominantly excitation of flexor neurones and excitation or inhibition in equal amounts of extensor cells. Dynamic fusimotor neurones were influenced in a strictly reciprocal manner with excitation of flexor cells and inhibition of extensor cells except for a few neurones which could not be reached from nucleur ruber. Evidence was also obtained indicating that the shortest path from nucleus ruber to static fusimotor neurones involves one interneurone.

Animals↗
PubMed1966

Action of static and dynamic fusimotor fibres on secondary endings of cat's spindles.

1. The effects exerted on secondary endings by repetitive stimulation of single static or single dynamic fusimotor fibres were studied in nine tenuissimus spindles in cats.2. The discharge of each secondary ending was recorded simultaneously with the discharge of the primary ending belonging to the same spindle.3. All the nineteen static fusimotor fibres studied activated secondary endings.4. Of eight dynamic fusimotor fibres, seven had no action on secondary endings. One dynamic fibre activated an atypical secondary ending which displayed some phasic sensitivity.5. No difference in conduction velocity was found between static and dynamic fibres.6. The implications of these observations for the mechanism of action of static and dynamic fusimotor fibres are discussed.

Animals↗
PubMedDate not supplied

Plasma interleukin-1 beta and sleep architecture in schizophrenia and other nonaffective psychoses.

OBJECTIVE: It has been reported that sleep deprivation may enhance interleukin (IL)-1 beta production of healthy subjects. Furthermore, patients with acute psychoses have been reported to exhibit higher levels of IL-1 beta than healthy controls. The present study examined polysomnographic sleep and morning IL-1 beta plasma values in 20 drug-free patients with acute nonaffective psychoses. METHODS: Ten patients with DSM-III diagnosis of schizophrenia, five with delusional disorder, and five with atypical psychosis underwent polysomnographic sleep registrations and their morning blood levels of IL-1 beta were measured. RESULTS: IL-1 beta values correlated negatively with the length of the sleep period (p = 0.010) and the relative time of rapid eye movement (REM) sleep (p = 0.038), and positively with REM latency (p = 0.043). CONCLUSIONS: It is concluded that reduced sleep, possibly especially reduced REM sleep, may be a reason for increased morning IL-1 beta values in these patients. Additional studies on IL-1 beta in psychiatric patients should consider the possibility of sleep disturbances as a possible explanation for deviations in IL-1 beta levels.

Adolescent↗