Modulatory role and mechanism of BDNF and its receptor TrkB in colonic motility disorder in chronic stress rat

Abstract

To investigate the role and mechanism of BDNF and its receptor TrkB in the disorder of colonic motility in chronic stress rats. A total of 20 male Wistar rats were randomly divided into two groups using to completely random method after weighed, with 10 rats in each group. Chronic water avoidance stress model was established. Then the fecal pellets of water avoidance stress (WAS) group and sham water avoidance stress (SWAS) group were recorded. Enzyme linked immunosorbent assay (ELISA), real time PCR, Western blot and immunohistochemistry were used to detect the expression of BDNF and TrkB in serum and colon muscle. The amplitudes of contractions of circular smooth muscle strips of each group were recorded after the treatment of TTX, BDNF and K252a. The number of fecal pellets had obviously increased in WAS group comparing with SWAS group (P < 0.05). The level of serum BDNF in WAS group was higher than that of SWAS group ((158.30 ± 9.82) vs (84.68 ± 7.80) pg/ml). And the expression of TrkB in the colon muscle in WAS group was higher than that in SWAS group (0.44 ± 0.03 vs 0.30 ± 0.02, P < 0.05). There was no significant difference between the two groups in expression of BDNF mRNA in colon muscle (P > 0.05). TrkB was mainly expressed in the cell nucleus of muscular layer neurons, and the expression of TrkB had obviously increased in WAS rats. The amplitudes of contractions of circular smooth muscle in WAS rats had significantly increased compared with SWAS rats ((0.35 ± 0.02) vs (0.22 ± 0.03) g, P < 0.05). After adding TTX to block the function of enteric nervous, the difference was remaining ((0.89 ± 0.07) vs (0.53 ± 0.06) g, P < 0.05). BDNF was added to the bath and the R value at different time was recorded. The difference had statistically significant at 6 min and 12 min (both P < 0.05). BDNF could induced the contraction peak of the circular smooth muscle. The contraction peak induced by BDNF was delayed and reduced when K252a was added to the bath 30 min before adding BDNF. BDNF plays a modulatory role in the disorder of colonic motility in chronic stress rat by acting on its receptor TrkB.