Developmental Characteristics of Neurons in the Intramural Ganglia of the Small Intestine Containing Different Types of Calcium-Binding Proteins

Immunohistochemical and morphometric methods were used to study the locations, relative contents, and cross-sectional areas of calbindin (CB)- and calretinin (CR)-immunopositive neurons in the intramural ganglia of the intermuscular plexus of the rat duodenum ( n = 37) during postnatal ontogeny (days 1, 10, 20, 30, and 60 and 1 and 2 years of age). CB- and CR-immunopositive neurons were detected in all the rats studied, from neonatal to aged. Proportions of CR-immunopositive neurons increased over the first 10 days of life and then showed no significant changes, including in aged animals. Proportions of CB-containing neurons increased to reach a maximum by day 20 of life, decreased insignificantly to day 30, and then remained without significant change. The mean sizes of CB- and CR-immunopositive neurons were significantly greater than the mean cross-sectional area of immunonegative neurons in all age groups.