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  • 1
    Electronic Resource
    Electronic Resource
    H-reflexes are less depressed following muscle stretch in spastic spinal cord injured patients than in healthy subjects (1993)
    Springer
    Experimental brain research 97 (1993), S. 173-176 
    Details
    ISSN: 1432-1106
    Keywords: Spinal cord ; H-reflexes ; Ia afferents ; Motoneurones ; Human
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The size of the soleus H-reflex was measured after a slow (17 deg/s) passive stretch of ankle plantarflex ors and compared to its control size without muscle stretch in ten neurologically healthy subjects and in six spastic spinal-cord-injured patients. Two seconds after the end of the stretch, the size of the H-reflex was reduced to about 30% of its pre-stretch size in the healthy sub jects. The depression remained for 10–15 s. In the spastic, spinal-cord-injured patients, stretch caused significantly less reduction in the size of the H-reflex. The H-reflex also regained its pre-stretch size much faster than in healthy subjects. We suggest that the smaller depression of the H-reflex observed in spastic patients may be involved in the pathophysiology of spasticity.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00228827
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  • 2
    Electronic Resource
    Electronic Resource
    Intrinsic membrane properties causing a bistable behaviour of α-motoneurones (1984)
    Springer
    Experimental brain research 55 (1984), S. 391-394 
    Details
    ISSN: 1432-1106
    Keywords: Spinal cord ; Motoneurones ; Bistable state ; Serotonin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary In decerebrate cats a train of impulses in Ia afferents may lead to a sustained increase in excitability of α-motoneurones of homonymous and heteronymous muscles. It was previously suggested that this long-lasting excitability increase reflects a maintained synaptic input to the motoneurones from excitatory interneurones. With intracellular recording from motoneurones we here demonstrate that the sustained increase of α-motoneurone activity is due to an all-or-none plateau depolarization. This plateau can be induced by a short train of excitatory synaptic potentials or a brief, intracellularly injected depolarizing current pulse and is terminated by a short train of inhibitory synaptic potentials or a hyperpolarizing current pulse. It is concluded that maintained motor unit firing triggered by a brief train of impulses in Ia afferent reflects an intrinsic bistable behaviour of α-motoneurones.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00237290
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Ca++ dependent bistability induced by serotonin in spinal motoneurons (1985)
    Springer
    Experimental brain research 57 (1985), S. 422-425 
    Details
    ISSN: 1432-1106
    Keywords: Spinal cord ; Motoneurons ; Bistable state ; Serotonin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The plateau potential, responsible for the bistable state of spinal motoneurons, recently described in the decerebrate cat, was suggested to depend on serotonin (Hounsgaard et al. 1984). In an in vitro preparation of the spinal cord of the turtle we now show that serotonin, applied directly to the bath, transforms the intrinsic response properties of motoneurons, uncovering a plateau potential and voltage sensitive bistability. The changes induced by serotonin were blocked by Mn++, while the plateau potential and the bistability remained after application of tetrodotoxin. We conclude that serotonin controls the expression of a Ca++ dependent plateau potential in motoneurons.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00236551
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  • 4
    Electronic Resource
    Electronic Resource
    Proprioceptive input resets central locomotor rhythm in the spinal cat (1987)
    Springer
    Experimental brain research 68 (1987), S. 643-656 
    Details
    ISSN: 1432-1106
    Keywords: Spinal cord ; Motoneurones ; Fictive locomotion ; Group I afferents ; Resetting ; Entrainment
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The reflex regulation of stepping is an important factor in adapting the step cycle to changes in the environment. The present experiments have examined the influence of muscle proprioceptors on centrally generated rhythmic locomotor activity in decerebrate unanesthetized cats with a spinal transection at Th12. Fictive locomotion, recorded as alternating activity in hindlimb flexor and extensor nerves, was induced by administration of nialamide (a monoamine oxidase inhibitor) and L-DOPA. Brief electrical stimulation of group I afferents from knee and ankle extensors were effective in resetting fictive locomotion in a coordinated fashion. An extensor group I volley delivered during a flexor burst would abruptly terminate the flexor activity and initiate an extensor burst. The same stimulus given during an extensor burst prolonged the extensor activity while delaying the appearance of the following flexor burst. Intracellular recordings from motoneurones revealed that these actions were mediated at premotoneuronal levels resulting from a distribution of inhibition to centres generating flexor bursts and excitation of centres generating extensor bursts. These results indicate that extensor group I afferents have access to central rhythm generators and suggest that this may be of importance in the reflex regulation of stepping. Experiments utilizing natural stimulation of muscle receptors demonstrate that the group I input to the rhythm generators arises mainly from Golgi tendon organ Ib afferents. Thus an increased load of limb extensors during the stance phase would enhance and prolong extensor activity while simultaneously delaying the transition to the swing phase of the step cycle.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00249807
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  • 5
    Electronic Resource
    Electronic Resource
    Development in neonatal rats of the sensory resetting of the locomotor rhythm induced by NMDA and 5-HT (1997)
    Springer
    Experimental brain research 114 (1997), S. 193-204 
    Details
    ISSN: 1432-1106
    Keywords: Key words Locomotion ; Central pattern generator ; Spinal cord ; Muscle afferents ; Neonatal rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  Developmental changes in the effects of quadriceps (Q) nerve stimulation on the locomotor rhythm induced by a mixture of N-methyl-d-aspartic acid and 5-hydroxytryptamine were examined using in vitro preparations from neonatal rats at postnatal days (P) 1–6. The effects of such stimulation on the rhythm were dependent both on stimulus strength and on the age of the animal. Low-intensity stimulation (≤3.0×T, where T=threshold for the monosynaptic reflex) during the flexor phase reset the rhythm via a prolongation of the flexor burst in most rats at P1–3, but via flexor burst truncation at P4–6. At any age, low-intensity stimulation during the extensor phase had no consistent effect on the ongoing rhythm. Activation of muscle afferents evoked via isometric contraction of the Q muscle caused effects similar to those obtained on low-intensity electrical stimulation in all age groups. In all age groups, high-intensity stimulation (≥5.0×T) caused resetting when delivered during the flexor phase via a prolongation of the flexor burst and during the extensor phase via a truncation of the extensor burst. These results suggest that the type of resetting evoked from low-threshold muscle afferents changes drastically during postnatal week1, while effects evoked from high-threshold afferents remain unchanged.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/PL00005628
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    Paper (German National Licenses)
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