Changes of intestinal sensitivity and Ghrelin levels in the physiological aging process of SD rats

Objective: To observe changes of intestinal sensitivity and Ghrelin levels in serum and brain-gut axis in the physiological aging process of SD rats. Methods: Twenty-four healthy SD rats were divided into four groups according to the age of three months, nine months, eighteen months and twenty-four months, respectively, with six rats in each group. Rectal saccule dilatation which can cause abdominal muscle contraction was applied. Intestinal sensitivity was estimated by the area under the curve (ANC) generated by muscle contraction. The contents of Ghrelin in serum and brain-gut axis were measured by ELISA. Results: (1) After rectal saccule dilatation, 3-month-old rats showed the smallest ANC, and the ANC was expanded with the increase of age, especially in the medium and high intensity of dilatation (all P<0.05). (2) Ghrelin level in serum was the lowest in the 3-month group and the highest in the 9-month group. After that, the serum level of Ghrelin tended to decrease, but without significant difference (P>0.05). (3) Ghrelin level in gastrointestinal tissues tended to increase gradually with age (all P<0.05), and the level in the same age group was as follows: the highest in the body of the stomach (P<0.01), followed by the jejunum and the ileum (P<0.05), and the lowest in the sigmoid colon and the rectum junction (P<0.05). Conclusion: Intestinal sensitivity of SD rats is increased in the process of physiological aging; Ghrelin level in serum is decreased and that in brain-gut axis is increased in the physiological aging process on the whole. These changes may cause gastrointestinal sensory and motor abnormalities, and are possibly involved in the occurrence and development of functional gastrointestinal disorders in old people.