Anatomic evidence for coexistence of cholinergic and adrenergic neurons in the developing human intestine: new aspects in the pathogenesis of developmental neuronal abnormalities.

In order to interpret the interrelation of cholinergic and adrenergic myenteric neural elements in the developing human, histochemical methods were used to demonstrate cholinergic and adrenergic activity independently in consecutive cryostat sections of the esophagus, ileocecal region, and colon of fetuses of 9 to 22 weeks ovulation age. At least some of the neural cells remained plastic, with respect to their transmitter choice, and showed both cholinergic and adrenergic function. These cells were shown to be present first in the ileocecal region (11 weeks) then in the esophagus (12 weeks) and lastly in the colon (14 weeks). Our findings support the hypothesis of a dual gradient of maturation of enteric neurons. The choice of transmitters is influenced by a "microenvironmental" factor, which may also arrest the maturation or cause the death of neurons.