Objective      To determine the expression profiles and distribution features of islet amyloid polypeptide (IAPP) and substance P (SP) in the rectum of rabbits during postnatal development.     Methods      Sixty rabbits were equally divided into 6 groups according to their age

5th-

15th-

25th-

35th-

60th- and 90th-day groups. Their rectum tissue were collected

fixed in Bouin solution

embedded in routine paraffin and then made into serial sections. The expressions of IAPP and SP were observed by immunohistochemical SABC staining and image analysis.     Results      In the 5th-day group

a few IAPP positive-cells were scattered into the mucosa epithelium of rectum. Since the 35th-day group

the number of IAPP positive-cells was ascended and obviously reached a peak in the 60th-day group (P0.05)

and then was descended from the 60th-day to 90th-day group (P0.05). The positive cells were mainly distributed in the connective tissue of tunica propria. The mean grey values of IAPP positive-cells were decreased gradually during the postnatal development period and reached the lowest in the 60th-day group (P0.05). However

SP positive-cells were first present in the rectum in the 15 days group

and the number of SP positive-cells were increased distinctly since 60th-day group(P0.05). The mean grey values of SP positive-cells were declined gradually from 60 days(P0.05).     Conclusion      The expression of IAPP and SP in the rectum is changed gradually during the postnatal development period，which suggested that both of them should participate in the process of adjusting in maturation of digestive function.