Related Experiment Video
Updated: Sep 25, 2026
Multi-system Monitoring for Identification of Seizures, Arrhythmias and Apnea in Conscious Restrained Rabbits
Published on: March 27, 2021
Electrocardiographic changes associated with the nasopharyngeal reflex in conscious rabbits: vago-sympathetic
E Nalivaiko1, C G De Pasquale, W W Blessing
1Department of Physiology, Centre for Neuroscience, Flinders University, Bedford Park, SA 5042, Australia. eugene.nalivaiko@flinders.edu.au
Abstract:
Electrocardiographic responses were assessed in conscious rabbits when the nasopharyngeal reflex was elicited by inhalation of formaldehyde vapour. There was a profound fall in heart rate (224+/-5 to 64+/-4 beats per min (bpm)) associated with abnormal or absent P-waves. There were no changes in the QRS complex. The R-T interval (control value 118+/-4 ms) was initially shortened to 107+/-3 ms and then prolonged to 130+/-4 ms. Heart rate and P-wave changes were prevented by muscarinic cholinergic blockade with methylscopolamine. The R-T shortening was reduced by 79+/-4% by beta-adrenergic blockade with propranolol. Methylscopolamine also unmasked small tachycardic responses (5-25 bpm) in 5/7 animals. This tachycardia was prevented by propranolol. Thus both parasympathetic vagal cardiac nerves and sympathetic cardiac nerves are activated during the nasopharyngeal reflex, with increased vagal effects in the sino-atrial node, and increased sympathetic effects in the ventricular myocardium.
