Locus coeruleus is a central chemoreceptive site in toads

Area of Science:

• Neuroscience
• Comparative Physiology
• Respiratory Regulation

Background:

• The locus coeruleus (LC) is a potential CO2 chemoreceptor in mammals.
• Its role in amphibian central chemoreception remains uninvestigated.
• This study explores the LC's function in toad (Bufo schneideri) chemosensitivity.

Purpose of the Study:

• To determine if the toad's LC acts as a CO2/H+ chemoreceptor site.
• To investigate the LC's involvement in respiratory and cardiovascular responses to hypercarbia.
• To elucidate the role of noradrenergic LC neurons in central chemosensitivity.

Main Methods:

• Used Fos immunoreactivity to detect LC activation by hypercarbia (5% CO2).
• Administered 6-hydroxydopamine lesions to assess noradrenergic LC neuron function.
• Microinjected solutions of varying pH (7.2-8.0) into the LC.

Main Results:

• Breathing 5% CO2 significantly increased c-fos-positive cells in the LC.
• LC lesions attenuated hypercarbia-induced ventilatory responses.
• Acidic microinjections (pH 7.2-7.6) into the LC increased ventilation.

Conclusions:

• The locus coeruleus in toads functions as a central CO2/H+ chemoreceptor.
• Noradrenergic LC neurons play a role in mediating respiratory responses to hypercarbia.
• These findings highlight the conserved role of the LC in respiratory control across vertebrates.