Role of brain-derived neurotrophic factor in the plasticity of enteric nervous-smooth muscle and its effects on gastrointestinal motility in mice / 中华消化杂志

ABSTRACT

Objective To observe the role of brain-derived neurotrophic factor (BDNF) in the plasticity of enteric nervous-smooth muscle system,and to investigate the effects of BDNF induced plasticity on gastrointestinal motility in mice.Methods Male hybrid BDNF knockout (BDNF+/) mice and wild type (BDNF+/+) mice were selected,eight in each group.Gastrointestinal motility of BDNF+/+ mice and BDNF+/ mice were tested and compared.Longitudinal muscle strips of mice colon smooth muscle were prepared.The effects of carbachol (1 × 10 5 mol/L) and BDNF (1 × 10 7 mol/L) on contractile function of muscle strips were observed.And the effects of tetrodotoxin (TTX,1 × 10-6 mol/L) on BDNF induced contractile function of muscle strips were also studied.The changes of the density of mice intestinal myenteric plexus and the expression of smooth muscle α-actin (α-SMA) in colon smooth muscle were detected by immunohistochemical techniqne.The ultrastruetural alterations of myenteric plexus,neuromuscular junction (NMJ) and smooth muscle cells were detected by transmission electron microscope (TEM).T-test or Rank sum test was performed for comparison between groups.Results Number of feces particles and water content in feces of BDNF+/-mice ((3.80±0.75) and (39.60±1.47)％) were both lower than those of BDNF+/+ mice ((6.30± 1.03) and (51.00± 1.61) ％),and the differences were statistically significant (t=4.792,12.827;both P＜0.05).Carbachol (1 × 10-5 mol/L) could significantly increase contraction activity of smooth muscle of BDNF+/+ mice (R =3.26 ± 0.43) and BDNF+/-mice (R=2.15 ± 0.36),and the difference was statistically significant (t=15.754,9.632;both P＜0.05).The effects on contraction exciting of smooth muscle strips of BDNF+/+ mice were more significant than BDNF+/ mice,and the difference was statistically significant (t =5.972,P＜0.05).BDNF could significantly increase contraction of muscle strips of BDNF+/+ mice and R value increased from 1 to 1.41±0.09,and the differences were statistically significant (t=13.674,P＜0.05).TTX could obviously inhibit the excitatory effects of BDNF,R value decreased from 1.41 ± 0.09 to 1.03 ± 0.04 (t=11.692,P＜0.05).The density of myenteric plexus of BDNF+/ mice (median 5.8％,interquartile range 4.2％-7.0％) was significantly lower than that of BDNF+/+ mice (median 9.0％,interquartile range 7.1％-10.8％),and the difference was statistically significant (Z =3.730,P＜ 0.05).The expression of α-SMA of BDNF+/-mice (median 33.4％,interquartile range 28.8％-38.5％) was significantly lower than that of BDNF+/+ mice (median 44.6％,interquartile range 39.2％-48.8％),and the difference was statistically significant (Z=4.565,P＜0.05).The results of TEM indicated ultrastructural alterations of myenteric plexus,NMJ and smooth muscle in BDNF+/-mice.Conelusionss BDNF could induce the plasticity of morphology and function in enteric nervous-smooth muscle system,which may play an important role in mice gastrointestinal motility.