Opioids modulate an emergent rhythmogenic process to depress breathing

Area of Science:

• Neuroscience
• Respiratory Physiology

Background:

• Mammalian neural circuits generate rhythmic motor behaviors like breathing, walking, and chewing.
• Breathing rhythm generation is localized to the preBötzinger Complex (preBötC) in the brainstem.

Purpose of the Study:

• Investigate the role of burstlets in inspiratory rhythmogenesis within the preBötC.
• Determine if respiratory depressants, such as opioids, modulate burstlet frequency.
• Explore the mechanisms underlying opioid-induced respiratory depression.

Main Methods:

• Utilized medullary slices from neonatal mice.
• Administered μ-opioid receptor (μOR) agonist DAMGO to observe effects on burstlet generation.
• Generated mice with genetic deletion of μORs in a specific glutamatergic preBötC subpopulation.
• Investigated the role of Substance P and inhibitory synaptic transmission blockade.

Main Results:

• The μ-opioid receptor (μOR) agonist DAMGO slowed burstlet generation in neonatal mouse medullary slices.
• Genetic deletion of μORs in a glutamatergic preBötC subpopulation abolished opioid-mediated depression of burstlets.
• The neuropeptide Substance P reduced opioidergic effects, while blockade of inhibitory synaptic transmission did not.

Conclusions:

• Inspiratory rhythmogenesis is an emergent process modulated by opioids, not solely dependent on strong motor output bursts.
• Burstlets represent a key component of the rhythmogenic process in the preBötC.
• Findings offer insights into ameliorating opioid-induced breathing depression.