AIM:To evaluate effects of preand postnatal protein deprivation and postnatal recovery on the myenteric plexus of the rat esophagus. METHODS: Three groups of young Wistar rats (aged 42 d) were studied: normalfed (N42), proteindeprived (D42), and proteinrecovered (R42). The myenteric neurons of their esophagi were evaluated by histochemical reactions for nicotinamide adenine dinucleotide (NADH), nitrergic neurons (NADPH)diaphorase and acetylcholinesterase (AChE), immunohistochemical reaction for vasoactive intestinal polypeptide (VIP), and ultrastructural analysis by transmission electron microscopy.RESULTS: The cytoplasms of large and medium neurons from the N42 and R42 groups were intensely reactive for NADH. Only a few large neurons from the D42 group exhibited this aspect. NADPH detected in the D42 group exhibited low reactivity. The AChE reactivity was diffuse in neurons from the D42 and R42 groups. The density of large and small varicosities detected by immunohistochemical staining of VIP was low in ganglia from the D42 group. In many neurons from the D42 group, the double membrane of the nuclear envelope and the perinuclear cisterna were not detectable. NADH and NADPH histochemistry revealed no group differences in the prof ile of nerve cell perikarya (ranging from 200 to 400 μm2).CONCLUSION: Protein deprivation causes a delay in neuronal maturation but postnatal recovery can almost completely restore the normal morphology of myenteric neurons. AIM: To evaluate effects of pre and postnatal protein deprivation and postnatal recovery on the myenteric plexus of the rat esophagus. METHODS: Three groups of young Wistar rats (aged 42 d) were studied: normalfed (N42), protein derived (D42), and proteinrecovered (R42). The myenteric neurons of their esophagi were evaluated by histochemical reactions for nicotinamide adenine dinucleotide (NADH), nitrergic neurons (NADPH) diaphorase and acetylcholinesterase (AChE), immunohistochemical reaction for vasoactive intestinal polypeptide (VIP), and ultrastructural analysis by transmission electron microscopy .RESULTS: The cytoplasms of large and medium neurons from the N42 and R42 groups were intensely reactive for NADH. Only a few large neurons from the D42 group were presented this NADPH detected in the D42 group showing low reactivity. The AChE reactivity was diffuse in neurons from the D42 and R42 groups. The density of large and small varicosities detected by immunohistochemical stainin g of VIP was low in ganglia from the D42 group. In many neurons from the D42 group, the double membrane of the nuclear envelope and the perinuclear cisterna were not detectable. NADH and NADPH histochemistry revealed no group differences in the prof ile of nerve cells perikarya ranging from 200 to 400 μm2. CONCLUSION: Protein deprivation causes a delay in neuronal maturation but postnatal recovery can almost completely restore the normal morphology of myenteric neurons.