J Neurogastroenterol Motil.  2014 Oct;20(4):423-446. 10.5056/jnm14092.

Colonic Migrating Motor Complexes, High Amplitude Propagating Contractions, Neural Reflexes and the Importance of Neuronal and Mucosal Serotonin

• Smith TK
• Park KJ
• Hennig GW

• KMID: 2381207
• DOI: http://doi.org/10.5056/jnm14092

Abstract

The colonic migrating motor complex (CMMC) is a critical neurally mediated rhythmic propulsive contraction observed in the large intestine of many mammals. It seems to be equivalent to the high amplitude propagating contractions (HAPCs) in humans. This review focuses on the probable neural mechanisms involved in producing the CMMC or HAPC, their likely dependence on mucosal and neuronal serotonin and pacemaker insterstitial cells of Cajal networks and how intrinsic neural reflexes affect them. Discussed is the possibility that myenteric 5-hydroxytryptamine (5-HT) neurons are not only involved in tonic inhibition of the colon, but are also involved in generating the CMMC and modulation of the entire enteric nervous system, including coupling motility to secretion and blood flow. Mucosal 5-HT appears to be important for the initiation and effective propagation of CMMCs, although this mechanism is a longstanding controversy since the 1950s, which we will address. We argue that the slow apparent propagation of the CMMC/HAPC down the colon is unlikely to result from a slowly conducting wave front of neural activity, but more likely because of an interaction between ascending excitatory and descending (serotonergic) inhibitory neural pathways interacting both within the myenteric plexus and at the level of the muscle. That is, CMMC/HAPC propagation appears to be similar to esophageal peristalsis. The suppression of inhibitory (neuronal nitric oxide synthase) motor neurons and mucosal 5-HT release by an upregulation of prostaglandins has important implications in a number of gastrointestinal disorders, especially slow transit constipation.

Keyword

5-HT neurons; Colon; Colonic Motor complex; Mucosa; Occult reflexes

MeSH Terms

Colon*
Constipation
Enteric Nervous System
Humans
Intestine, Large
Mammals
Motor Neurons
Mucous Membrane
Myenteric Plexus
Myoelectric Complex, Migrating*
Neural Pathways
Neurons*
Nitric Oxide
Peristalsis
Prostaglandins
Reflex*
Serotonin*
Up-Regulation
Nitric Oxide
Prostaglandins
Serotonin