Breathing response of the tegu lizard to 1–4% CO2 in the mouth and nose or inspired into the lungs

Ballam, G. O.

doi:10.1016/0034-5687(85)90092-1

Cited by 26 publications

(2 citation statements)

References 17 publications

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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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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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“…Transient apnoea can be induced by directing low concentrations of CO2 into the upper airways of amphibians and reptiles (Smyth, 1939;Boelaert, 1941;MS 9889 D. BARTLETT JR, S. L. KNUTH AND J. C. LEITER Sakakibara, 1978). The response in tegu lizards and garter snakes has been analysed recently, and found to depend on afferents in the olfactory nerves (Ballam, 1985; Coates & Ballam, 1989). Thus these animals can smell C02 in low concentrations, and when they do so, breathing is inhibited.…”

Section: Introductionmentioning

confidence: 99%

Alteration of ventilatory activity by intralaryngeal CO2 in the cat.

Bartlett

Knuth

Leiter

1992

The Journal of Physiology

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SUMMARY1. We investigated the responses of phrenic and hypoglossal nerve activities to the addition of 3, 5 and 10% CO2 to a constant flow of warm, humidified air through the isolated upper airway in decerebrate, paralysed, artificially ventilated cats.2. In bilaterally vagotomized animals, intralaryngeal CO2 caused a dose-related decrease in peak integrated phrenic activity. This response became attenuated with time, but was still discernible after 3 min of continuous intralaryngeal CO2. In the same experiments, intralaryngeal CO2 caused a gradual increase in peak integrated hypoglossal nerve activity.3. Intermittent pulsing of intralaryngeal CO2 during neural inspiration or expiration resulted in similar, but smaller decreases in the phrenic activity of some animals. Hypoglossal activity was not influenced appreciably by this procedure.4. Systemic hypercapnia attenuated the phrenic responses to intralaryngeal CO2.The hypoglossal responses were greatly reduced or abolished. 5. In vagally intact cats, ventilated by a servo-respirator in accordance with phrenic nerve activity, intralaryngeal CO2 resulted in only a trace of reduction in phrenic discharge. After bilateral vagotomy, the same animals showed typical responses, as described above.6. All responses to intralaryngeal CO2 were abolished after bilateral section of the superior laryngeal nerves (SLNs).7. We conclude that intralaryngeal CO2 acts by way of receptors with afferents in the SLNs to decrease phrenic and increase hypoglossal nerve activities. The responses are not importantly gated during neural inspiration or expiration. The responses to intralaryngeal CO2 are most clearly demonstrable after bilateral vagotomy, suggesting that vagal mechanisms serve to stabilize respiratory motor neural activity in intact animals.

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