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  • 1
    Electronic Resource
    Electronic Resource
    Effects of inhibitory neurotransmitters on the mudpuppy (Necturus maculatus) locomotor pattern in vitro (1999)
    Springer
    Experimental brain research 129 (1999), S. 172-184 
    Details
    ISSN: 1432-1106
    Keywords: Key words GABA ; Glycine ; Central pattern generator ; Spinal cord ; Locomotion ; In vitro
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  Effects of inhibitory neurotransmitters on the locomotor rhythm and pattern generation were investigated using an in vitro preparation isolated from the mudpuppy (Necturus maculatus). The preparation consisted of the first five segments of the spinal cord and the right forelimb attached by the brachial nerves. During N-methyl-d-aspartate (NMDA)-induced locomotion, the rhythmic motor output (EMG) was recorded unilaterally from elbow flexor and extensor muscles. While neither glycine nor γ-aminobutyric acid (GABA)-related substances induced locomotion in the absence of NMDA, they modulated NMDA-induced locomotion. Bath application of glycine and GABA suppressed the rhythmic motor pattern induced by NMDA. Addition of glycine receptor antagonist strychnine or GABAA receptor antagonist bicuculline disrupted the phase relationship between antagonistic motor pools during ongoing locomotion, thereby changing the normal alternating pattern into synchronous EMG bursts. Both the GABAA receptor agonist muscimol and GABAB receptor agonist baclofen mimicked the effects of GABA as they either slowed down or stopped locomotion. Nipecotic acid, a GABA uptake blocker, had a similar effect. This suggested that an endogenous release of GABA modulated the locomotor rhythm. The endogenous release was antagonized by the GABAA and GABAB receptor antagonists bicuculline and CGP-35348, respectively. Immunocytochemistry revealed that glycine and GABA-positive neurons and fibers were present in mudpuppy spinal cord. Although the GABAergic neurons were more numerous than glycinergic neurons, both cell types contributed processes directed towards the white matter and occasionally towards the ependymal lining of the central canal. Our results suggest that inhibitory neurotransmitters exert powerful actions upon the neuronal network governing forelimb locomotion in the mudpuppy. The effects we observed may be mediated by a network of segmentally distributed glycinergic and GABAergic spinal neurons.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002210050887
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  • 2
    Electronic Resource
    Electronic Resource
    Reflexes induced by nerve stimulation in walking cats with implanted cuff electrodes (1978)
    Springer
    Experimental brain research 32 (1978), S. 213-224 
    Details
    ISSN: 1432-1106
    Keywords: Nerve stimulation ; Cuff electrodes ; Locomotion ; Cats
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Neural cuffs, implanted around various hindlimb nerves (sural, common peroneal, posterior tibial), were used to deliver brief stimulus trains to unrestrained cats walking on a treadmill. The resulting perturbations of the step cycle were evaluated by analyzing the EMG bursts recorded from the ankle extensors and by high speed cinematography. It was found that relatively weak stimulation (1.4 to 2 X T) of the posterior tibial nerve was very effective in eliciting a prolongation of the flexion phase provided the stimuli were applied just prior to the expected onset of the ankle extensor EMG burst. This ipsilateral hyperflexion was correlated with a prolongation of the contralateral extension. The same stimuli applied during stance usually evoked a yielding of the stimulated leg and a prolongation of the ongoing contralateral stance. In addition to these flexor and extensor reflex effects, it was found that low threshold stimulation of the sural and common peroneal nerves resulted in a powerful reflex activation of the ankle extensors. In contrast, stimulation of the gastrocnemius-soleus nerve (a muscle nerve) produced no discernible behavioral effects, even for stimuli at 3 X T, indicating that the observed reflexes are probably mediated by cutaneous afferents. The results were largely confirmed in experiments using the same cuffs implanted in spontaneously walking premammillary cats.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00239728
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  • 3
    Electronic Resource
    Electronic Resource
    Serotonergic modulation of the mudpuppy (Necturus maculatus) locomotor pattern in vitro (1996)
    Springer
    Experimental brain research 111 (1996), S. 57-67 
    Details
    ISSN: 1432-1106
    Keywords: 5-HT ; Locomotion ; Motor control ; Pattern generation ; Spinal cord ; Mudpuppy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The aims of the present study were to: (1) study the role of serotonin (5-HT) in modulating the central pattern generator (CPG) underlying locomotion in the mudpuppy (Necturus maculatus); (2) investigate whether there is an intrinsic spinal serotonergic system. These aims were achieved by the use of pharmacological and immunocytochemical methods. To study modulation of the locomotor pattern and rhythm, we applied 5-HT, its uptake blocker zimelidine, and a variety of 5-HT receptor agonists and antagonists to an in vitro brainstemspinal cord preparation isolated from the mudpuppy. The preparation consisted of the first five segments of the spinal cord and the right forelimb attached by the brachial plexus. The spinal CPG for locomotion was activated chemically by adding NMDA to the superfusing solution. During locomotion, bipolar electromyographic (EMG) recordings were made unilaterally from flexor and extensor ulnae muscles. 5-HT on its own did not induce locomotion, but it did have a profound modulatory effect on NMDA-induced locomotion. 5-HT produced a dose-dependent increase in the overall cycle duration and enhanced the EMG burst duration. Use of zimelidine indicated that there is an endogenous release of 5-HT which modulated the locomotor rhythm. The endogenous release was antagonized by 5-HT1/5-HT2 receptor antagonist methiothepin. Immunocytochemical analysis, in which the entire spinal cord of the mudpuppy was used, revealed that there were more than one type of spinal serotonergic neuron. They were differentiated according to the cell diameter, shape, and arborization pattern of their processes. These neurons were located within the central gray matter ventrolateral to the central canal. Our results suggest that 5-HT plays an important role in modulating the locomotor CPG in the mudpuppy, by acting through a well-developed spinal serotonergic system. This is in contrast to what has been reported in higher vertebrates, where serotonergic innervation is derived from supraspinal structures.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00229556
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  • 4
    Electronic Resource
    Electronic Resource
    Contribution of peripheral afferents to the activation of the soleus muscle during walking in humans (1991)
    Springer
    Experimental brain research 87 (1991), S. 679-687 
    Details
    ISSN: 1432-1106
    Keywords: Stretch reflex ; Locomotion ; Human
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Small, rapid stretches were applied to the soleus muscle during the stance phase of walking by lifting the forefoot with a pneumatic device. Stretch responses were induced in the soleus muscle by the disturbance. The amplitude and time course of the responses from the soleus muscle were a function of both the kinematics of the disturbance and the time in the step cycle when the disturbance was applied. The step cycle was divided into 16 equal time parts, and data obtained within each of these parts were averaged together. The electromyographic (EMG) response of the soleus muscle showed a time course that was similar to the time course of the angular velocity induced by the disturbance at the ankle. Three linear equations were used to predict the EMG response from the soleus muscle as a function of the angular kinematics of the disturbance: 1) velocity, 2) velocity and displacement, 3) velocity, displacement and acceleration. Introduction of a pure delay between the EMG and the kinematics substantially improved the predictions. Most of the variance (70%) in the EMG response could be accounted for by the velocity of the disturbance alone with an optimal delay (average 38 ms). Inclusion of a displacement term significantly increased the variance accounted for (85%), but further addition of an acceleration term did not. Since the velocity of the disturbance accounted for most of the variance, the reflex gain was estimated from the velocity coefficient. This coefficient increased in a ramp-like fashion through the early part of the stance phase, qualitatively similar to the increase in the H-reflex. Based on these identified gains, this reflex pathway was estimated to contribute substantially (30% to 60%) to the activation of the soleus muscle particularly during the early part of the stance phase.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00227094
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  • 5
    Electronic Resource
    Electronic Resource
    A comparison of intact and in-vitro locomotion in an adult amphibian (1992)
    Springer
    Experimental brain research 88 (1992), S. 609-614 
    Details
    ISSN: 1432-1106
    Keywords: Locomotion ; Glycine ; NMDA ; Central pattern generation ; Amphibian
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Locomotion was compared in an intact and invitro preparation of the adult mudpuppy (Necturus maculatus) The intact animals walked on an aquatic treadmill while in-vitro preparations were made to walk with a bath application of the excitatory amino acid NMA (N-methyl DL-aspartate). EMG recordings of shoulder muscles (pectoralis, latissimus dorsi, dorsalis scapulae, and procoracohumeralis) and elbow muscles (brachialis and extensor ulnae) were obtained from intact animals while recordings were made from only the elbow muscles in-vitro. The invitro preparation required magnesium in the bath to initiate and maintain locomotion, consistent with an NMDA mediated response. Also consistent with an NMDA response was the finding that glycine potentiated the NMA induced locomotion in-vitro. The range of cycle durations seen in-vitro was well within the range seen in the intact animal, while gait analysis demonstrated the similarity of intact and in-vitro locomotor cycles. In spite of these very similar locomotor patterns there are interesting differences in the patterned output seen invitro, such as the absence of a second burst in the brachialis muscle in-vitro.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00228189
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    Paper (German National Licenses)
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