Changes in respiratory functions during metamorphosis of the bullfrog, Rana catesbeiana

Aldosterone, corticosterone, and thyroid hormone and their influence on respiratory control development in Lithobates catesbeianus: An in vitro study

“…Note that the higher HCO 3 − used for adults is based on values reported for whole blood (Toews and Stiffler, 1990) and the aCSF composition used in other laboratories working on this species (Winmill et al, 2005;Reid et al, 2000). The superfusate was equilibrated with a 98% O 2 /2% CO 2 gas mixture and had a pH 7.90 ± 0.10 which corresponds to normal blood pH in this species (Just et al, 1973;. The brainstem was finally transected between the optic tectum and the forebrain and then caudal to the hypoglossal nerve before being transferred to the recording chamber coated with Syglard (Dow Corning; Midland, MI, USA) where it was immobilized with insect pins ventral side up.…”

“…With metamorphosis, the progressive use of the lungs for gas exchange results in CO 2 retention (Just et al, 1973) and consequently, tadpole development has been linked with the emergence of CO 2 /pH chemosensitivity as an important source of respiratory drive (Torgerson et al, 1997;Milsom, 2010). Though attractive, this hypothesis is debatable.…”

Developmental changes in central O2 chemoreflex in Rana catesbeiana: the role of noradrenergic modulation

“…The use of a higher bicarbonate concentration in the aCSF for adult bullfrogs is common (e.g. Winmill et al, 2005) and is based on the fact that (1) during bullfrog development, the transition from water to air breathing is associated with a respiratory acidosis, which is compensated by renal HCO 3 -retention (Just et al, 1973), (2) the blood-brain barrier of frog is permeable to HCO 3 - (Wright, 1972) and (3) increasing aCSF results in a more stable respiratory activity in preparations from adult bullfrogs (Kinkead et al, 1994). The superfusate was equilibrated with a 98% O 2 /2% CO 2 gas mixture to pH·7.90±0.15 for tadpoles and pH·7.8±0.15 for adult bullfrogs (Kinkead et al, 1994;Torgerson et al, 1997).…”

Neonatal maturation of the hypercapnic ventilatory response and central neural CO2 chemosensitivity

“…Aquatic animals usually have low PCO 2 levels (~3-5 mmHg), and hypercapnia does not modify the pattern of fictive gill ventilation in the isolated tadpole brainstem preparation (Taylor et al, 2003a,b). As metamorphosis progresses, the blood PCO 2 rises in tadpoles (Just et al, 1973), and the frequency of bursts of lung-related cranial nerve activity in the isolated tadpole brainstem also increases and lung bursts begin to occur in clusters. Further, hypercapnia stimulates lung burst activity but not gill bursting activity (Taylor et al, 2003a,b).…”