The Bötzinger complex as the pattern generator for retching and vomiting in the dog

Area of Science:

• Neuroscience
• Physiology
• Gastroenterology

Background:

• The precise location of the neural circuitry controlling the emetic reflex (vomiting) has been a subject of investigation.
• Understanding the pattern generator for vomiting is essential for developing treatments for nausea and related disorders.

Purpose of the Study:

• To systematically identify and map the brainstem structures responsible for generating the emetic act.
• To elucidate the neural pathways involved in transmitting emetic signals from afferent nerves to the central pattern generator.

Main Methods:

• Decerebrate, paralyzed dogs were used to isolate brainstem functions.
• Systematic electrical stimulation and surgical transection of specific brainstem regions (e.g., solitary tract nucleus, Bötzinger complex) were performed.
• Electrophysiological recordings from relevant muscle nerves (phrenic, vagus, etc.) monitored emetic responses.

Main Results:

• Stimulation of several bulbar structures, including the solitary tract nucleus (NTS) and the Bötzinger complex (BOT), elicited emetic responses.
• Lesion studies indicated that the pathway involves rostral brainstem structures descending through the solitary complex (SC) to the subpostrema.
• Neurons in the subpostrema appear to project to the BOT, which acts as the pattern generator for the emetic act.

Conclusions:

• The Bötzinger complex (BOT) in the brainstem is identified as a critical component of the pattern generator for the emetic act.
• A proposed pathway involves vagal afferents entering the brainstem, descending via the solitary complex (SC) to the subpostrema, and then projecting to the BOT.
• These findings provide a detailed map of the neural circuitry underlying vomiting, with implications for antiemetic drug development.