Journal of Comparative Physiology B

, Volume 155, Issue 5, pp 571–575 | Cite as

Modification of vagal action on the toad heart by changes in flow

  • Gillian P. Courtice
  • D. I. McCloskey
Article
  • 38 Downloads

Summary

Hearts of toads (Bufo marinus) were perfused in situ with oxygenated Ringer's solution. The flow of the perfusate was varied during periods of vagal stimulation and in the absence of vagal stimulation. Pulse interval and cardiac contraction were monitored, and results only from those animals that showed no change in pulse interval with changes in flow in the absence of vagal stimulation were used. In these animals, during vagal stimulation, cardiac slowing was greater when flow was low than when it was high. In addition, in cases where vagal stimulation caused atrio-ventricular block, the block could be reversed by an increase in flow of the perfusate. The results are consistent with flow through the heart being an important determinant of the concentration of neurally released ACh at the pacemaker sites and therefore of the effectiveness of the vagus nerve.

Keywords

Vagus Nerve Vagal Stimulation Pulse Interval Sinus Venosus Tension Record 

Abbreviation

ACh

acetylcholine

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Copyright information

© Springer-Verlag 1985

Authors and Affiliations

  • Gillian P. Courtice
    • 1
  • D. I. McCloskey
    • 1
  1. 1.School of Physiology and PharmacologyUniversity of New South WalesSydneyAustralia

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