Multiple neural oscillators and muscle feedback are required for the intestinal fed state motor program

Area of Science:

• Gastroenterology
• Neuroscience
• Physiology

Background:

• The fed state in the gastrointestinal tract features segmentation, a motor pattern crucial for digestion and nutrient absorption.
• Segmentation involves rhythmic local constrictions in the intestine, essential for nutrient processing.
• The enteric nervous system (ENS) regulates segmentation, with intrinsic sensory neurons (ISNs) playing a key role.

Purpose of the Study:

• To investigate the enteric circuits regulating intestinal segmentation.
• To understand the role of intrinsic sensory neurons (ISNs) and their after-hyperpolarizing potentials (AHPs) in segmentation.
• To model the neural control of segmentation patterns.

Main Methods:

• In vitro experiments on guinea-pig jejunum using blockers of AHPs (TRAM-34, clotrimazole).
• Induction of segmentation with luminal decanoic acid.
• Development of a computational model of ENS circuits and muscle activity.

Main Results:

• Depressing AHPs increased contractile episode durations but did not affect burst frequency or quiescent periods.
• Computational model predicted feedback from circular muscle to ISNs is necessary for alternating activity and quiescence.
• Model suggested distinct synaptic transmission pathways from ISNs to excitatory and inhibitory motor neurons.

Conclusions:

• Two rhythm generators control segmentation: one for contractions within bursts, another for burst occurrence.
• The occurrence of segmentation bursts depends on ISN AHPs and feedback from circular muscle contractions.
• This study elucidates the neural mechanisms underlying segmentation, essential for gastrointestinal function.