Innervation of the alimentary tract in Chondrostean fish (Acipenseridae). A histochemical, microspectro-fluorimetric and ultrastructural study.

In the enteric nervous system of Chondrostean fish, green and yellow fluorescent nerve fibers were revealed by the glyoxylic acid histochemical method. The yellow fluorescent fibres were found in the circular muscle layer and the green ones in the longitudinal layer and between the two muscle layers. Strongly fluorescent enterochromaffin cells were observed in all parts of the alimentary tube in the epithelium of the mucosa. Yellow fluorescent nerve fibres and enterochromaffin cells showed the peak emission at 520-525 nm, which corresponds to that of serotonin fluorophore in a model system. Green fluorescent nerve fibres had their emission maximum at 460-470 nm, which corresponds to that of dopamine and noradrenaline. According to the vesicular population, different nerve fibres were observed in all parts of the alimentary tube under the electron microscope.