A decrease in nasal CO2 stimulates breathing in the tegu lizard

Coates, E. L.; Furilla, Robert A.; Ballam, G. O.; Bartlett, D.

doi:10.1016/0034-5687(91)90040-p

Cited by 15 publications

(2 citation statements)

References 6 publications

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“…Since the ventilatory response to hypercarbia involves both stimulation and inhibition from CO 2 -sensitive chemoreceptors, and this balance shows variability in a population (Figure 3) (Coates et al, 1991).…”

Section: Reassessment Of the Hypercarbic Ventilatory Response In Adulmentioning

confidence: 99%

Reassessment of chemical control of breathing in undisturbed bullfrogs, Lithobates catesbeianus, using measurements of pulmonary ventilation

Santin

Hartzler

2016

Respiratory Physiology & Neurobiology

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Despite the importance of bullfrogs (Lithobates catesbeianus) as models in respiratory control, chemical control of breathing in conscious bullfrogs has never been assessed with methods that measure the tidal volume (VT). This has precluded the calculation of important respiratory variables like minute ventilation (V.E) and air convection requirement. To address this, we adapted airflow pneumotachography for use in bullfrogs and reassessed chemical control of breathing. We show that V.E measured with pneumotachography produces breathing pattern and metabolism values consistent with anurans. Second, we confirm that bullfrogs have small ventilatory responses to hypercarbia that include increases in tidal volume and a post-hypercarbic hyperpnea. We observed that the magnitude of the post-hypercarbic hyperpnea does not depend on ventilatory responses during hypercarbia. Finally, we showed that increases in breathing frequency and VT during hypoxia are differentially regulated with time. These findings comprise the first complete assessment of hypercarbic and hypoxic V.E responses in intact bullfrogs and emphasize the importance of measuring VT.

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Section: Reassessment Of the Hypercarbic Ventilatory Response In Adulmentioning

confidence: 99%

Reassessment of chemical control of breathing in undisturbed bullfrogs, Lithobates catesbeianus, using measurements of pulmonary ventilation

Santin

Hartzler

2016

Respiratory Physiology & Neurobiology

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“…The sensitivity of pulmonary stretch receptors (which are mildly CO 2 sensitive) is depressed by hypercapnia, which reduces the negative feedback during lung inflation, and results in elevated V T (Milsom, 1995;Powell et al, 1988). In addition, hypercapnic stimulation of pulmonary and upper airway chemoreceptors has been shown to reduce f (and hence V E ) in tegus (Ballam, 1985;Ballam and Donaldson, 1988;Coates et al, 1991). Whether gestation induces any alterations in the sensitivity of CO 2 chemoreceptors in lizards is unclear.…”

Section: Breathing Patterns In Response To Hypercapniamentioning

confidence: 99%

Gestation increases the energetic cost of breathing in the lizard, Tiliqua rugosa

Munns

2012

Journal of Experimental Biology

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SUMMARYHigh gestational loads result in fetuses that occupy a large proportion of the body cavity and may compress maternal organs. Compression of the lungs results in alterations in breathing patterns during gestation, which may affect the energetic cost of breathing. In this study, the energetic cost of breathing during gestation was determined in the viviparous skink Tiliqua rugosa. Radiographic imaging showed progressive lung compression during gestation and a 30% reduction in the lung inflation index (rib number at which the caudal margin of the lung was imaged divided by total rib number). Pneumotachography and open flow respirometry were used to measure breathing patterns and metabolic rates. Gestation induced a twofold increase in minute ventilation via increases in breathing frequency, but no change in inspired tidal volume. The rates of O 2 consumption and CO 2 production did not change significantly during gestation. Together, these results suggest that a relative hyperventilation occurs during gestation in T. rugosa, which in turn suggests that diffusion and/or perfusion limitations may exist at the lung during gestation. The energetic cost of breathing was estimated as a percentage of resting metabolic rate using hypercapnia to stimulate ventilation at different stages of pregnancy. The energetic cost of breathing in non-pregnant lizards was 19.96±3.85% of resting metabolic rate and increased threefold to 62.80±10.11% during late gestation. This significant increase in the energetic cost of breathing may have significant consequences for energy budgets during gestation.

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