Evidence that a cyclic rise in avian pulmonary co2 triggers the next inspiration

Ventilation, Gaseous Exchange and Air Sac Gases During Moderate Thermal Panting in Domestic Fowl

“…However, it is known that CO2 is involved in the control of normal breathing in birds via central and systemic chemoreceptors and also directly by its effects on the neural discharge of intrapulmonary chemoreceptors (see review by Bouverot, 1978). Intrapulmonary chemoreceptors are known to be specifically sensitive to intrapulmonary PCO, Barnas, Mather & Fedde, 1978) and are thought to be capable of adjusting respiratory pattern on a breath-to-breath basis (Miller & Kunz, 1977;Scheid, Gratz, Powell & Fedde 1978;Berger, Tallman & Kunz, 1980;Tallman & Kunz, 1982). Available evidence suggests the intrapulmonary chemoreceptors are located most abundantly in the area of the mediodorsal secondary bronchi (Burger, Osborne & Banzett, 1974;.…”

Acta XVII Congressus internationalis ornithologici, Berlin, 5.-11.VI.1978 /

“…They demonstrated that the ventilatory rhythm of an awake, unidirectionally ventilated chicken will synchronize with oscillating intrapulmonary CO2 concentrations over a ränge of Va to 2 times the normal frequency of breathing (Kunz & Miller, 1971Kunz et ah, 1973). Respiration in the chicken can be paced by a variety of CO2 waveforms, and evidence suggests that the rise in intrapul¬ monary CO2 concentration, which would act to inhibit the discharge of IPCs, is the important event that tnggers onset of the subsequent breath (Miller & Kunz, 1977, Kunz & Tallman, 1978. Although other chemoreceptors may also be influenced by the oscillations in intrapulmonary CO2 concentrations, it is likely that the IPCs are most directly involved with the response.…”

Blood gases and respiratory pattern in exercising fowl: comparison in normoxic and hypoxic conditions

“…Recent studies on the respiratory responses of ducks (Kiley, Kuhlmann & Fedde, 1979 and domestic fowl (Brackenbury, Gleeson & Avery, 1982;Brackenbury & Gleeson, 1983, 1986 exercised on treadmills have provided information about factors that govern changes in the rate and depth of breathing during spontaneous hyperpnea. It is clear that the respiratory rhythm generator is highly sensitive to variations in intrapulmonary and arterial Pco • Experiments on anaesthetized birds have demonstrated the importance of specifically CO2-sensitive intrapulmonary chemoreceptors (IPCs) in the regulation of breathing pattern (Miller & Kunz, 1977;Tallman & Kunz, 1982;Tallman & Grodins, 1982) and the results from the exercise studies support this role. In chickens it has been suggested that the IPCs regulate the depth of breathing in order to match lung ventilation to CO2 flux across the respiratory epithelium, thereby preserving normal arterial P C o (Gleeson, Haigh, Molony & Anderson, 19856).…”