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Journal of Comparative Physiology A

, Volume 197, Issue 1, pp 75–88 | Cite as

A central pacemaker that underlies the production of seasonal and sexually dimorphic social signals: anatomical and electrophysiological aspects

  • Laura QuintanaEmail author
  • Paula Pouso
  • Gabriela Fabbiani
  • Omar Macadar
Original Paper

Abstract

Our long-term goal is to approach the understanding of the anatomical and physiological bases for communication signal diversity in gymnotiform fishes as a model for vertebrate motor pattern generation. Brachyhypopomus gauderio emits, in addition to its electric organ discharge (EOD) at basal rate, a rich repertoire of rate modulations. We examined the structure of the pacemaker nucleus, responsible for the EOD rate, to explore whether its high output signal diversity was correlated to complexity in its neural components or regional organization. We confirm the existence of only two neuron types and show that the previously reported dorsal–caudal segregation of these neurons is accompanied by rostral–caudal regionalization. Pacemaker cells are grouped dorsally in the rostral half of the nucleus, and relay cells are mainly ventral and more abundant in the caudal half. Relay cells are loosely distributed from the center to the periphery of the nucleus in correlation to somata size. Our findings support the hypothesis that regional organization enables a higher diversity of rate modulations, possibly offering distinct target areas to modulatory inputs. Since no anatomical or electrophysiological seasonal or sexual differences were found, we explored these aspects from a functional point of view in a companion article.

Keywords

Electric fish Medullary nucleus Communication Brachyhypopomus gauderio CPG 

Abbreviations

EO

Electric organ

EOD

Electric organ discharge

Cd

Caudal

CV

Coefficient of variation

Dr

Dorsal

EBST

Electromotor bulb spinal tract

PM

Pacemaker neurons

PN

Pacemaker nucleus

PPNc

Diencephalic prepacemaker chirp region

R

Relay neurons

Rt

Rostral

sPPN

Sublemniscal prepacemaker

Vt

Ventral

Notes

Acknowledgments

We wish to thank Omar Trujillo, Kent Dunlap and Phil Stoddard for their generous revision and suggestions to our manuscript. We thank Catherine Carr for her valuable comments and Amalia Dutra, Hugo Peluffo and Angel Caputi who very kindly donated antibodies used in this study. We are grateful to Rossana Perrone and Ana Silva who performed the behavioral experiments and participated in all field trips. All procedures with animals were performed in accordance with the guidelines of the local ethical committee (Comisión Honoraria de Experimentación Animal, CHEA, Universidad de la República, Uruguay). This research was financed by PDT 043 and PEDECIBA.

Supplementary material

3D representation of the PN of Brachyhypopomus gauderio. In a frontal view the PN is tilted slightly counter clockwise. Rostral: indicated with a star. Red pacemaker cells, cyan relay cells.

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Copyright information

© Springer-Verlag 2010

Authors and Affiliations

  • Laura Quintana
    • 1
    Email author
  • Paula Pouso
    • 1
    • 2
  • Gabriela Fabbiani
    • 1
    • 3
  • Omar Macadar
    • 1
  1. 1.Dpto de NeurofisiologíaInstituto de Investigaciones Biológicas Clemente EstableMontevideoUruguay
  2. 2.Dpto de Histología y Embriología, Facultad de MedicinaUniversidad de la RepúblicaMontevideoUruguay
  3. 3.Dpto de Neurofisiología Celular y MolecularInstituto de Investigaciones Biológicas Clemente EstableMontevideoUruguay

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