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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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    Paper (German National Licenses)
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  • 2
    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
    Library Location Call Number Volume/Issue/Year Availability
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    Paper (German National Licenses)
    Fulltext
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