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  • 1
    Digitale Medien
    Digitale Medien
    Springer
    Experimental brain research 111 (1996), S. 296-304 
    ISSN: 1432-1106
    Schlagwort(e): Spasticity ; Stretch reflex ; Spinal cord ; l-dopa ; Monoamines ; Human
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: 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.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 2
    ISSN: 1432-1106
    Schlagwort(e): Spinal interneurones ; Spinal reflexes ; Monoamines
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary The actions of noradrenaline (NA) and 5-hydroxytryptamine (5-HT; serotonin) were compared with those of L-3,4-dihydroxyphenylalanine methyl ester (Methyl-L-DOPA) on transmission to spinal interneurones in mid-lumbar (L4 and L5) segments of the cat spinal cord. The drugs were applied ionophoretically and their effects were tested on monosynaptic field potentials evoked by nerve impulses in hindlimb group I and group II muscle afferent fibres and on responses of interneurones with synaptic input from these fibres. Of field potentials recorded at various locations, both NA and 5-HT depressed those evoked from group II fibres in the intermediate and ventral horn regions of the spinal cord but not, or only occasionally, in the dorsal horn. Field potentials of group I origin were not depressed. The tested interneurones were located where group II field potentials were affected. NA, 5-HT and Methyl-L-DOPA depressed responses to electrical stimulation of group II fibres but not responses evoked by group I fibres. The depression consisted of an increase in the latency and a decrease in the number of action potentials evoked by the stimuli. All three drugs were also found to decrease the amplitude of intracellularly recorded monosynaptic EPSPs of group II origin but not of monosynaptic EPSPs evoked in the same neurones by group I fibres. Interneuronal firing induced by DL-homocysteic acid was depressed as effectively as responses to electrical stimulation of peripheral nerves. The possibility of presynaptic and/or postsynaptic mechanisms of the selective depression of synaptic actions of group II origin are discussed.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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