Postnatal changes in enteric plexus axonal thickness

Chronological age has not always been an accurate predictor of gut motility in newborns. We hypothesized that the enteric plexus is immature at birth. We studied whole-mount preparations of the myenteric plexus in pigs from mid-point of gestation to adulthood.

Distal large bowel whole-mount preparations of the myenteric plexus were stained using ACHE histochemistry in five pigs from six different age groups (60 and 90 days gestation, newborn, 4 and 12 weeks old, and adult pigs). With the aid of light micrographs and Image J program the axonal diameter, distance between ganglia, neuronal size and neuronal nucleus size were measured. Statistical significance was measured using one-way ANOVA test.

There was significant increase in axonal diameter and interganglionic distance, with increasing age in the myenteric plexus of rectum in pigs (P < 0.05). Neuronal cell size and nucleus size of the enteric neurons also increased with age, but was not statistically significant.

This study shows for the first time that the axonal thickness in the enteric myenteric plexus undergoes striking changes during the first 12 weeks of life in piglets. Assessment of axonal thickness in rectal biopsies may be a valuable morphological feature in diagnosing functional intestinal obstruction in infants.