Pre-Bötzinger complex functions as a central hypoxia chemosensor for respiration in vivo

Area of Science:

• Neuroscience
• Respiratory Physiology
• Chemosensation

Background:

• The pre-Bötzinger complex (pre-BötC) is identified as the primary respiratory rhythm generator in the brainstem.
• Previous studies showed that activating excitatory amino acid receptors in the pre-BötC elicits diverse respiratory responses, including gasp-like patterns.
• Hypoxia, a state of low oxygen, is known to induce gasping, but the precise neural substrates remain under investigation.

Purpose of the Study:

• To investigate the chemosensitivity of the pre-BötC to hypoxia.
• To determine if focal hypoxia within the pre-BötC can modulate respiratory output and induce gasp-like patterns.

Main Methods:

• Experiments were conducted on anesthetized, vagotomized, paralyzed, and mechanically ventilated cats.
• The pre-BötC was functionally identified using DL-homocysteic acid (DLH) microinjections.
• Unilateral microinjections of sodium cyanide (NaCN) were used to induce focal hypoxia in the pre-BötC, and phrenic nerve discharge was recorded.

Main Results:

• Microinjection of NaCN into the pre-BötC resulted in excitation of phrenic nerve discharge in a significant proportion of tested sites (49/81).
• The augmented inspiratory output manifested as gasp-like bursts, tonic excitation, augmented eupneic breaths, or altered burst frequency.
• These findings demonstrate that focal hypoxia within the pre-BötC can directly augment respiratory output.

Conclusions:

• The study identifies a specific locus within the brainstem (pre-BötC) that is intrinsically chemosensitive to hypoxia.
• The results support the hypothesis that the respiratory rhythm generator in the pre-BötC possesses hypoxic chemosensitivity.
• This intrinsic chemosensitivity of the pre-BötC may play a crucial role in the generation of gasping behavior during severe systemic hypoxia.