DIFFERENTIATION OF ENTERIC PLEXUSES AND INTERSTITIAL-CELLS OF CAJAL IN THE RAT GUT DURING PRENATAL AND POSTNATAL LIFE

The stomach, small and large intestine of fetuses at term, of unfed ne wborns, of suckling, weaning and of adult rats were studied by a combi ned light (LM) and electron microscope (EM) examination. Neuron-specif ic enolase was used as a neuronal marker under LM, Zinc-iodide-osmium (ZIG) impregnation was used for a selective staining of neurons and in terstitial cells of Cajal under both LM and EM. A routine EM procedure made it possible to identify the nerve elements and ICC and to evalua te their degree of differentiation. The differentiation of enteric ple xuses and ICC was poor at birth and was accomplished during the weanin g period, The myenteric plexus differentiation preceded the submucous plexus differentiation; in particular, under both LM and EM myenteric neurons were already recognizable in the fetus, while the submucous ne urons by day 0 under EM and by day 7 under LM. The ICC were poorly dif ferentiated at birth and acquired the adult morphology during the suck ling period, Nerve endings contacting ICC were differentiated before I CC differentiation. The ZIO uptake by both nerve elements and ICC corr elated with the establishment of their differentiated features. In con clusion, the present findings confirmed that differentiation of ICC an d enteric plexuses is microenvironment dependent, since their differen tiative steps are interrelated and correlated with diet changes, ZIO i mpregnation under EM enabled a distinction to be made between a 'morph ological' and a 'functional' differentiation, and revealed that the fo rmer is achieved during the suckling period and the latter by the wean ing period, It can be suggested that during the postnatal developmenta l stages ICC and neuronal functions might be different from those in a dulthood.