The distribution of presumptive thoracic paraganglionic tissue in the common marmoset (Callithrix jacchus)

An open-source tool for automated analysis of breathing behaviors in common marmosets and rodents

The respiratory system maintains homeostatic levels of oxygen (O2) and carbon dioxide (CO2) in the body through rapid and efficient regulation of breathing frequency and depth (tidal volume). The commonly used methods of analyzing breathing data in behaving experimental animals are usually subjective, laborious, and time-consuming. To overcome these hurdles, we optimized an analysis toolkit for the unsupervised study of respiratory activities in animal subjects. Using this tool, we analyzed breathing behaviors of the common marmoset (Callithrix jacchus), a New World non-human primate model. Using whole-body plethysmography in room air as well as acute hypoxic (10% O2) and hypercapnic (6% CO2) conditions, we describe breathing behaviors in awake, freely behaving marmosets. Our data indicate that marmosets' exposure to acute hypoxia decreased metabolic rate and increased sigh rate. However, the hypoxic condition did not augment ventilation. Hypercapnia, on the other hand, increased both the frequency and depth (i.e., tidal volume) of breathing.

Electrical stimulation of the rabbit pulmonary artery increases respiratory output

This study was conducted to test the hypothesis that the pulmonary artery is involved in neural respiratory control and to identify the involved topographical region, if any. Six adult rabbits were anesthetized, artificially ventilated, and the chest was opened. The outer surface of the extra-pulmonary portion of the pulmonary artery was electrically stimulated by monitoring phrenic nerve activity. Phrenic nerve activity increased in three of the six rabbits when the proximal dorsal surface of the pulmonary trunk was stimulated. This positive response was abolished after bilateral vagotomy. In histological examinations we found densely grouped cells, i.e. pulmonary glomic tissue, with a fine nerve bundle in the tissue adjacent to the dorsal surface of the pulmonary trunk where electrical stimulation elicited respiratory augmentation. We suggest that there is a neural substrate which is involved in respiratory control inside the wall of or in the region adjacent to the proximal dorsal surface of the pulmonary trunk. Further studies to anatomically identify the neural substrate and clarify its physiological role in respiratory control are necessary.