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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Experimental brain research 1 (1966), S. 338-358 
    ISSN: 1432-1106
    Keywords: EPSPs ; IPSPs ; Interneurones ; Spinal cord
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Intracellular recording has been made in spinal cats from more than 100 interneurones in the dorsal horn and intermediary region of the lumbosacral spinal cord. The majority of interneurones receive not only EPSPs but also IPSPs from primary afferents. The IPSPs are evoked from three different systems, group I muscle afferents (probably Ib), low threshold cutaneous afferents and the FRA. The shortest central latency of the IPSPs indicates a disynaptic linkage from primary afferents. Interneurones with monosynaptic EPSPs from group I muscle afferents may receive IPSPs from all the above mentioned afferent systems. Interneurones with monosynaptic EPSPs from cutaneous afferents receive their inhibition from the two latter afferent systems. Convergence of EPSPs and IPSPs from the FRA may occur on the same interneurone. The results are discussed mainly with respect to inhibitory interaction between spinal reflex pathways.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Experimental brain research 111 (1996), S. 296-304 
    ISSN: 1432-1106
    Keywords: Spasticity ; Stretch reflex ; Spinal cord ; l-dopa ; Monoamines ; Human
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Antispastic effects of the noradrenaline and dopamine precursor l-3,4-dihydroxyphelanine (l-dopa) were investigated in 11 subjects in which exaggerated stretch reflexes developed after spinal cord injuries. The effects were evaluated from changes in the electromyographic (EMG) response of the quadriceps muscle during tendon jerks evoked by standardized taps over the patellar tendon, in clonus and in resistance to passive movements of the limb. After administration of l-dopa, EMG responses occurring 30–150 ms after the tendon tap decreased to about 50% of control, and clinical tests revealed a marked decrease in the resistance to muscle stretches and in the degree of clonus. The effects were maximal within about 1 h. The depressive actions of l-dopa are interpreted as being exerted primarily at the spinal level, since they were evoked in paraplegics and tetraplegics. The results support the previous hypothesis that group II muscle afferents contribute to the exaggerated stretch reflex in spastic patients because l-dopa depresses transmission from group II but not from group I muscle afferents. They also indicate the possibility of using l-dopa in the treatment of spastic patients.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1432-1106
    Keywords: Stimulation ; Spinal cord ; Propriospinal neurones ; Lumbosacral motoneurones
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Stimulation of the lateral funicle was performed at different segmenta levels in the cat in order to investigate the connecxions of long propriospinal neurones with ipsilateral lumbosacral motoneurones and interneurones projecting directly to them. In one series of experiments the propriospinal contribution was assessed from the difference between the effect of maximal stimulation in C 1 (activating supraspinal descending fibres) and in more caudal segments (activating supraspinal and propriospinal fibres). In another series on cats with chronic hemisection in C 3 pure propriospinal effects were evoked by stimulation of the thoracic spinal cord. In both series it was shown that volleys in long propriospinal neurones evoke monosynaptic EPSPs and disynaptic EPSP and/or IPSP in many flexor and extensor motoneurones; an extracellular monosynaptic focal synaptic potential was recorded in lamina VII of Rexed. The effects evoked by stimulation of the Th 11 segment after chronic C 3 hemisection were not found after chronic Th 10 hemisection. It is therefore tentatively suggested that they were due to stimulation of long descending propriospinal neurones originating in the lower cervical and upper thoracic segments, their axon trajectory being in the middle of the lateral funiculus and conduct at velocity 100 m/sec. Other effects evoked by stimulation of Th 11 after chronic Th 10 hemisection are ascribed to antidromic activation of axons of ascending neurones.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Experimental brain research 71 (1988), S. 447-449 
    ISSN: 1432-1106
    Keywords: L-DOPA ; Spinal cord ; Spinal interneurones
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Methyl-L-DOPA (L-beta-3,4-dihydroxyphenylalanine methyl ester, hydrochloride) was applied ionophoretically to investigate its effects on neurones at various locations in the cat spinal cord. Its actions were tested on monosynaptic field potentials evoked from group I and group II muscle afferents in midlumbar segments. Methyl-L-DOPA has been found to depress field potentials evoked from group II afferents in the ventral horn and in the intermediate zone but not in the dorsal horn, nor field potentials evoked from group I afferents. Its effects were the same as those of systemically applied L-DOPA (L-beta-3,4-dihydroxyphenylalanine), although weaker.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Experimental brain research 105 (1995), S. 25-38 
    ISSN: 1432-1106
    Keywords: Cuneiform nucleus ; Synaptic transmission ; Spindle afferents ; Spinal cord ; Cat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The effects of short trains of electrical stimuli applied within the cuneiform nucleus and the subcuneiform region were examined on transmission from group I and group II muscle afferents to first-order spinal neurons. Variations in the effectiveness of transmission from these afferents were assessed from changes in the sizes of the monosynaptic component of extracellular field potentials evoked following stimulation of muscle nerves. Field potentials evoked from group II muscle afferents in the dorsal horn of the midlumbar and sacral segments and in the intermediate zone of the midlumbar segments were reduced when the test stimuli applied to peripheral nerves were preceded by conditioning stimulation of the cuneiform nucleus or the subcuneiform region. The depression occurred at conditioning-testing intervals of 20–400 ms, being maximal at intervals of 32–72 ms for dorsal horn potentials and 40–100 ms for intermediate zone potentials. At the shortest intervals, both group II and group I field potentials in the intermediate zone were depressed. Conditioning stimulation of the cuneiform nucleus depressed group II field potentials nearly as effectively as conditioning stimulation of the coerulear or raphe nuclei. We propose that the nonselective depression of transmission from group I and II afferents at short intervals is due to the activation of reticulospinal pathways by cells or fibers stimulated within the cuneiform area. We also propose that the selective depression of transmission from group II afferents at long intervals is mediated at least partly by monoaminergic pathways, in view of the similarity of the effects of conditioning stimulation of the cuneiform nucleus and of the brainstem monoaminergic nuclei and by directly applied monoamines (Bras et al. 1990). In addition, it might be caused by primary afferent depolarization mediated by non-monoaminergic fibers (Riddell et al. 1992).
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Experimental brain research 100 (1994), S. 1-6 
    ISSN: 1432-1106
    Keywords: Spinal cord ; Ascending tracts ; Spinocervical neurons ; Group II muscle afferents ; Cat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Peripheral input to spino-cervical tract (SCT) neurons located in the L4 and L5 segments of the cat spinal cord was investigated using both extracellular and intracellular recording. The main aim was to find out whether midlumbar SCT neurons are excited monosynaptically not only by cutaneous afferents but also by group II muscle afferents, as in the sacral segments but apparently not in the caudal lumbar segments. Input from group II muscle afferents was found in 73% of investigated neurons; the latencies of excitation by group II afferents were compatible with a monosynaptic coupling between these afferents and 62% of neurons. The majority of the midlumbar SCT neurons were excited by group II afferents of the quadriceps and deep peroneal nerves. The predominant monosynaptic input from cutaneous afferents to the same neurons was from the saphenous nerve.
    Type of Medium: Electronic Resource
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