Central CO2 chemoreception in developing bullfrogs: anomalous response to acetazolamide

Area of Science:

• Physiology
• Neuroscience
• Comparative Biology

Background:

• Central chemoreception is vital for regulating breathing.
• Carbonic anhydrase plays a role in CO(2) sensing.
• Metamorphosis in amphibians involves significant physiological changes.

Purpose of the Study:

• To investigate central CO(2) chemoreception in Rana catesbeiana tadpoles and frogs.
• To assess the role of carbonic anhydrase using acetazolamide.
• To examine developmental changes in chemosensory responses during metamorphosis.

Main Methods:

• Recorded buccal and lung rhythms from cranial nerve VII and spinal nerve II.
• Administered acetazolamide (25 microM) during normocapnia and hypercapnia.
• Analyzed responses across different developmental stages (early, mid, late metamorphosis).

Main Results:

• Acetazolamide mimicked hypercapnic responses in early/mid-stage tadpoles and frogs.
• Acetazolamide inhibited hypercapnic responses in late-stage tadpoles.
• Hypercapnia and acetazolamide decreased buccal frequency but not duty cycle.

Conclusions:

• The hypercapnic response involves increased lung ventilation and decreased buccal ventilation.
• Acetazolamide's effect is inconsistent during metamorphosis, limiting its use in chemoreceptor studies.
• Late-stage metamorphosis may involve reorganized chemosensory processes for aquatic-to-aerial transition.