The objective of this work was to analyze the morphoquantitative behavior of neurons of the myenteric plexus, as well as the morphometry of elements of the proximal colon wall of Wistar rats (Rattus norvegicus) fed a normoproteic (22%) and a hypoproteic (8%) diet, and sacrificed at 360 days of age. To perform the neuronal evaluation, we used whole-mount preparations of the proximal colon immunostained with the antibody anti-myosin-V. The neurons were quantified in 80 microscopic fields (16.98 mm(2)/animal). The neuronal cell body morphometry was performed in 100 neurons/animal. Samples of the proximal colon were weighed and measured, and then submitted to routine histological processing. They were later stained using the hematoxylin--eosin method in order to carry out morphometric analysis on the mucosa and external muscular layers. The number of neurons and the neuronal cell body morphometry did not present significant differences between the studied groups. A significant reduction in the weight and length of the proximal colon and in mucosa layer thickness was observed in the animals fed with the hypoproteic diet. We concluded that the neuronal and non-neuronal components of the proximal colon adapted to the imposed nutritional condition, which guaranteed the maintenance of their functions.