Chloride Modulates Central pH Sensitivity and Plasticity of Brainstem Breathing-Related Biorhythms in Zebra Finch Embryos.

All terrestrial vertebrate life must transition from aquatic gas exchange in the embryonic environment to aerial or pulmonary respiration at birth. In addition to being able to breathe air, neonates must possess functional sensory feedback systems for maintaining acid-base balance. Respiratory neurons in the brainstem act as pH sensors that can adjust breathing to regulate systemic pH.

Development and regulation of breathing rhythms in embryonic and hatchling birds.

For many, if not all, air-breathing vertebrates, breathing-like movements begin while the embryo is still ensconced in an aqueous environment. This is because primordial regions of the CNS become spontaneously active during early gestation and then must functionally transform and specialize once air breathing commences. The degree to which the embryonic ventilatory control system is established and competent at birth is variable, however, even between different components of the respiratory system.