Functional and Structural Investigation of Myenteric Neurons in the Human Colon

The enteric nervous system independently controls gastrointestinal function including motility, which is primarily mediated by the myenteric plexus, therefore also playing a crucial role in functional intestinal disorders. Live recordings from human myenteric neurons proved to be challenging due to technical difficulties. Using the neuroimaging technique, we are able to record human colonic myenteric neuronal activity and investigate their functional properties in a large cohort of patients.

Activity from myenteric neurons in wholemount preparations of different sampling sites of fresh, human colonic tissue was recorded using neuroimaging with the voltage sensitive dye 1-(3-sulfanatopropyl)-4-[beta[2-(di-n-octylamino)-6-naphthyl]vinyl]pyridinium betaine. Neuronal responses were analyzed following stimulation with nicotine and serotonin (5-HT) for differences based on the donor's age, the disorder indicative for surgery and the colonic region. Immunohistochemistry was performed to calculate the total neuronal numbers.

Stimulation with nicotine and 5-HT elicited reproducible action potential discharge in a proportion of human myenteric neurons. The responses to 5-HT were significantly greater in tissues from older patients and from those with inflammatory disorders, while neuronal activity to nicotinergic stimulation was comparable in all patients. Neuronal numbers declined with rising patient's age and was highest in the sigmoid colon.

Neuroimaging with 1-(3-sulfanatopropyl)-4-[beta[2-(di-n-octylamino)-6-naphthyl]vinyl]pyridinium betaine was successfully adapted to record reproducible responses from human colonic myenteric neurons upon pharmacological stimulation. Evidence exists for an impact of age and inflammation on the serotonergic neuronal signaling and for differences in neuronal numbers in the distinct colonic regions as well as a neuronal decrease with age.