Effects Of BDNF-TrkB On Chronic Visceral Hypersensitivity Caused By Neonatal Maternal Separation

ObjectiveTo explore the effect of BDNF-TrkB on central sensitization of chronic visceral hypersensitivity in rats with neonatal maternal separation.MethodsA rat model with chronic visceral hypersensitivity was established by neonatal maternal separation(NMS)for 3 h daily during post-natal days 3-21,and each one were put in cubicles separately.(1)Responses of the abdominal muscle to colorectal distention(CRD,40 and 60 mmHg)were measured to evaluate the visceral hypersensitivity in rats when they were adult(8-10weeks).(2)Effects of TrkB on visceral hypersensitivity were examined by the intrathecal injection of ANA-12(5-20 mM).(3)The expressions of BDNF and TrkB receptor of spinal thoracolumbar and lunbosacral segment were tested by Western blot.(4)Expressions of mRNA of TrkB in spinal TL and LS segment were detected using qRT-PCR technique(5)The effects of time of ANA-12 on visceral hypersensitivity were observed.(6)The expressions of spinal PKMζ were compared between pre-administration and post-administration ANA-12 by Western Blot.(7)Open field test was used to examine whether ANA-12 had side effects on movement and emotion.Results(1)The amplitude ratios of EMG to CRD were significantly increased in rats with chronic visceral hypersensitivity when compared with those in control rats(P < 0.05).(2)Intrathecal injection of ANA-12(a TrkB selective inhibitor)dose-dependently attenuated the chronic visceral hypersensitivity in NMS rats,but no effect on control rats(P < 0.05).(3)The expression of BDNF and TrkB receptor in spinal TL and LS segments was significantly increased in NMS rats when compared with control rats(P< 0.05).(4)The mRNA expression of TrkB in spinal TL and LS segments was significantly increased in NMS rats when compared with control rats(P < 0.05).(5)The maximal inhibition was observed at the time point of 30 min and significant inhibition lasted for 150 min after ANA-12 effective dose application under 40 and60 mmHg CRD in NMS rats.(6)The expression of PKMζ in spinal TL and LS segments was significantly decreased after intrathecal injection of ANA-12(P < 0.05).(7)ANA-12 had no significant effect on the movement(P > 0.05),but had significant effect on emotion in control and NMS rats(P < 0.05),which indicated ANA-12 had no obvious side effects.ConclusionSpinal BDNF-TrkB could play an important role in visceral hypersensitivity in rats with NMS.