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  • Bladder-sphincter dyssynergia  (1)
  • Repetitive firing  (1)
  • 1
    Electronic Resource
    Electronic Resource
    On the regulation of repetitive firing in lumbar motoneurones during fictive locomotion in the cat (1992)
    Springer
    Experimental brain research 90 (1992), S. 441-455 
    Details
    ISSN: 1432-1106
    Keywords: Afterhyperpolarisation ; Motoneurone ; Fictive locomotion ; Repetitive firing ; Cat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Repetitive firing of motoneurones was examined in decerebrate, unanaesthetised, paralysed cats in which fictive locomotion was induced by stimulation of the mesencephalic locomotor region. Repetitive firing produced by sustained intracellular current injection was compared with repetitive firing observed during fictive locomotion in 17 motoneurones. During similar interspike intervals, the afterhyperpolarisations (AHPs) during fictive locomotion were decreased in amplitude compared to the AHPs following action potentials produced by sustained depolarising current injections. Action potentials were evoked in 10 motoneurones by the injection of short duration pulses of depolarising current throughout the step cycles. When compared to the AHPs evoked at rest, the AHPs during fictive locomotion were reduced in amplitude at similar membrane potentials. The post-spike trajectories were also compared in different phases of the step cycle. The AHPs following these spikes were reduced in amplitude particularly in the depolarised phases of the step cycles. The frequency-current (f-I) relations of 7 motoneurones were examined in the presence and absence of fictive locomotion. Primary ranges of firing were observed in all cells in the absence of fictive locomotion. In most cells (6/7), however, there was no relation between the amount of current injected and the frequency of repetitive firing during fictive locomotion. In one cell, there was a large increase in the slope of the f-I relation. It is suggested that this increase in slope resulted from a reduction in the AHP conductance; furthermore, the usual elimination of the relation is consistent with the suggestions that the repetitive firing in motoneurones during fictive locomotion is not produced by somatic depolarisation alone, and that motoneurones do not behave as simple input-output devices during this behaviour. The correlation of firing level with increasing firing frequency which has previously been demonstrated during repetitive firing produced by afferent stimulation or by somatic current injection is not present during fictive locomotion. This lends further support to the suggestion that motoneurone repetitive firing during fictive locomotion is not produced or regulated by somatic depolarisation. It is suggested that although motoneurones possess the intrinsic ability to fire repetitively in response to somatic depolarisation, the nervous system need not rely on this ability in order to produce repetitive firing during motor acts. This capability to modify or bypass specific motoneuronal properties may lend the nervous system a high degree of control over its motor output.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00230927
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Evidence for a strychnine-sensitive mechanism and glycine receptors involved in the control of urethral sphincter activity during micturition in the cat (1998)
    Springer
    Experimental brain research 119 (1998), S. 297-306 
    Details
    ISSN: 1432-1106
    Keywords: Key words Spinal inhibition ; Interneurons ; Micturition ; Bladder-sphincter dyssynergia ; Cat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  Micturition in the decerebrate cat is characterized by a coordinated bladder contraction and a simultaneous decrease in external urethral sphincter (EUS) efferent activity. Without the suppression of EUS activity, voiding is significantly impaired, resulting in a state sometimes referred to as bladder-sphincter dyssynergia. The aim of the present study was to determine whether glycinergic inhibition contributes to the suppression of EUS activity during micturition evoked by bladder distension or electrical stimulation of the pontine micturition center (PMC) in decerebrate cats. Using subconvulsive intravenous doses of strychnine (0.1–0.24 mg/kg), we examined changes in bladder and EUS electroneurographic (ENG) activity during micturition. Following subconvulsive doses of strychnine, tonic EUS ENG activity increased during bladder filling in five of six animals. In the presence of strychnine, it was possible to evoke reflex bladder contractions of similar duration and peak pressure to those observed before strychnine administration. However, there was an absence of suppression of EUS ENG activity during the bladder contractions in all the animals. To determine whether the changes in sphincter activity could be due to strychnine acting at glycine receptors on EUS motoneurons, sacral spinal tissue was processed for a structural protein (gephyrin) associated with the glycine receptor. Motoneurons in Onuf′s nucleus in S1 were identified using choline acetyltransferase immunohistochemistry and subsequently processed with a gephyrin monoclonal antibody. Abundant gephyrin labeling was evident throughout Onuf′s nucleus. Since Onuf′s nucleus is made up of EUS and other motoneuron populations, a sample of antidromically identified urethral and anal sphincter motoneurons were intracellularly labeled with tetramethylrhodamine dextran (TMR-D) and then processed with the gephyrin antibody. Using dual-beam confocal microscopy, gephyrin immunoreactivity was observed on the soma and proximal processes of individual EUS motoneurons in both male and female animals. It was concluded that a strychnine-sensitive mechanism contributes to the suppression of sphincter activity normally observed during voiding. Although glycinergic inhibition may affect several components of the circuitry responsible for micturition, it appears that the suppression of EUS motoneurons during micturition may be partly due to a direct glycinergic inhibition of the EUS motoneurons.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002210050345
    Library Location Call Number Volume/Issue/Year Availability
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    Paper (German National Licenses)
    Fulltext
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