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Journal of Comparative Physiology A

, Volume 181, Issue 2, pp 143–151 | Cite as

Mauthner cell-evoked synaptic actions on pacemaker medullary neurons of a weakly electric fish

  • A. Falconi
  • D. Lorenzo
  • S. Curti
  • F. R. Morales
  • M. Borde
ORIGINAL PAPER

Abstract

The present study was designed to examine the synaptic events in neurons of the pacemaker nucleus of Gymnotus carapo during the increase in rate of the electric organ discharge following activation of Mauthner cells. Pacemaker and relay cells were investigated using intracellular recordings which were performed under two different conditions: (1) with the pacemaker nucleus spontaneously discharging and (2) after its activity was abolished by anesthesia. Mauthner axon activation induced an increase in the rate of pacemaker cell discharges. This response was accompanied by an increase in the slope of the pacemaker potential (up to 110%) and a depolarization of these cells. The discharges of relay cells followed one to one those of pacemaker cells. In contrast to that observed in pacemaker cells, only brief depolarizing antidromic effects could be evoked in relay cells after Mauthner axon activation. In quiescent pacemaker cells, Mauthner cell activation induced a prolonged (up to 500 ms) depolarizing potential with an average amplitude of 1.92 ± 0.82 mV; its latency was 4.43 ± 1.14 ms. Our data indicate that, within the pacemaker nucleus, the population of pacemaker cells is the only target for Mauthner cell-evoked, short-latency excitatory synaptic actions.

Key words Pacemaker nucleus Pacemaker neurons Electric organ discharge Mauthner-cell Weakly electric fish 

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Copyright information

© Springer-Verlag Berlin Heidelberg 1997

Authors and Affiliations

  • A. Falconi
    • 1
  • D. Lorenzo
    • 2
  • S. Curti
    • 1
  • F. R. Morales
    • 1
  • M. Borde
    • 1
  1. 1.Laboratorio de Neurofisiología Celular, Dpto. de Fisiología, Facultad de Medicina, Facultad de Ciencias, Gral. Flores 2125, 11800 Montevideo- Uruguay Tel.: +598-2 943544; Fax: +598-2 948784 e-mail: mborde@fmed1.fmed.edu.ugUY
  2. 2.Division Neurofisiología, Instituto de Investigaciones Biológicas C. Estable, Av. Italia 3318, 11600 Montevideo, UruguayUY

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