Distinct generators for aspiration and expiration reflexes: localization, mechanisms and effects

Area of Science:

• Neuroscience
• Respiratory Physiology

Background:

• Two distinct airway defensive reflexes, the spiration reflex (AspR) and expiration reflex (ExpR), were recently described in juvenile rats.
• These reflexes involve distinct generators for inspiration (I) and expiration (E).

Purpose of the Study:

• To compare the AspR and ExpR in adult cats with previously described reflexes in rats.
• To investigate the brainstem control mechanisms underlying these distinct respiratory reflexes.

Main Methods:

• Re-evaluation of c-Fos-like immuno-reactive studies in cats.
• Brainstem transection/lesion experiments in anesthetized, non-paralyzed cats.

Main Results:

• The retro-trapezoid nucleus/parafacial respiratory group, the E generator in rats, is also activated during ExpR in cats.
• Brainstem transection above the obex eliminated the E generator and ExpR but preserved the I generator (pre-Bötzinger Complex) and AspR.
• The AspR in cats, particularly during asphyxic gasping, suggests a common brainstem circuit for both gasping and the gasp-like AspR.

Conclusions:

• Distinct I and E generators exist in cats, similar to rats, with the I generator contributing to AspR.
• The AspR and ExpR are controlled by distinct, multilevel brainstem mechanisms, supporting a dual control theory of respiration.
• These reflexes provide models for studying respiratory rhythm and pattern generation, with AspR linked to auto-resuscitation and ExpR to laryngeal chemoreflexes.