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  • 1
    Electronic Resource
    Electronic Resource
    Spatial distribution of the medullary command signal within the electric organ of Gymnotus carapo (1993)
    Springer
    Journal of comparative physiology 173 (1993), S. 221-226 
    Details
    ISSN: 1432-1351
    Keywords: Electric fish ; Pacemaker nucleus ; Electric organ activation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract The pacemaker nucleus of Gymnotus carapo contains two types of neurons: pacemaker cells which set up the frequency of the electric organ discharge (EOD) and relay cells which convey the command signal to the spinal cord. Direct activation of a single relay cell provides enough excitation to discharge a pool of spinal electromotor neurons and electrocytes, generating a small EOD (unit EOD). Different relay cells generate unit EODs of variable size and waveform, indicating the involvement of different groups of electrocytes. A special technique of EOD recording (multiple air-gap) was combined with intracellular stimulation of relay cells to study the spatial distribution within the electric organ (EO) of the command signal arising from different relay cells. Three types of relay cells could be identified: type I commanding the rostral 10% of the EO, type II which distribute their command all along the EO and type III driving the caudal 30%. Waveform analysis of unit EODs indicates that doubly innervated electrocytes which are the most relevant for attaining the specific EOD waveform, receive a favored command from the pacemaker nucleus.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00192980
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Electric organ activation in Gymnotus carapo: Spinal origin and peripheral mechanisms (1993)
    Springer
    Journal of comparative physiology 173 (1993), S. 227-232 
    Details
    ISSN: 1432-1351
    Keywords: Electric fish ; EOD ; Waveform
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract A new technique of multiple-air-gap recording was developed to study the EO activation process in Gymnotus carapo. Using this technique, the spatiotemporal pattern of electromotive force generation was investigated in normal and spinal-lesioned animals. Our data indicate that the EOD may be considered as the result of the sequential activation of 3 defined portions of the EO: the abdominal portion (included in the rostral 25% of the fish body), the central portion (comprising the intermediate 50% of the fish body) and the tail portion (the caudal 25% of the fish body). The EOD generated at each portion is characterized by: 1) timing respect to the pacemaker nucleus discharge, 2) speed of progression within the region, 3) waveform, and 4) magnitude. Spinal sections demonstrated that EMNs serving relatively small portions of the EO are widely distributed (convergence) and that surgical exclusion of relatively small portions of the spinal cord diminishes the amplitude of the EOD along an extended portion of the EO (divergence).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00192981
    Library Location Call Number Volume/Issue/Year Availability
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    Paper (German National Licenses)
    Fulltext
  • 3
    Electronic Resource
    Electronic Resource
    Spinal mechanisms of electric organ discharge synchronization in Gymnotus carapo (1990)
    Springer
    Journal of comparative physiology 167 (1990), S. 447-452 
    Details
    ISSN: 1432-1351
    Keywords: Electric fish ; Electric organ synchronization ; Spinal conduction velocities
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The duration of the electric organ discharge (EOD) in Gymnotus carapo is brief and independent of fish size. Spinal mechanisms involved in electrocyte synchronization were explored by recording spontaneous action potentials of single fibers from the electromotor bulbospinal tract (EBST). Using the field potential of the medullary electromotor nucleus (MEN) as a temporal reference we calculated the orthodromic conduction velocity (CV) of these fibers (range: 10.7–91 m/s). The CVs (in m/s) of fibers recorded at the same level of the spinal cord were significantly different in small and large fish; this difference disappeared when CV were expressed as percentage of body length/ms. Plotting these values against conduction distance (also in %) showed that low CV fibers predominate in the rostral cord while only fast fibers are found at distal levels. Moreover, antidromic stimulation of the distal cord was only effective on high CV fibers. The orthodromic CVs in the distal portion of the recorded fibers were calculated by collision experiments; no significant differences were found between proximal and distal portions. The spatial distribution of CV values within the EBST is proposed to play the main role in synchronizing the electromotoneurons' activity along the spinal cord.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00192581
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
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