The Role Of Hippocampal NSF In Chronic Visceral Pain

Objective Previous studies show that the roles of hippocampal PKMζ in the central sensitization of irritable bowel syndrome(IBS)like rats.In this study,the relationship of hippocampal N-ethylmaleicimide sensitive factors(NSF)with PKMζ in IBS-like rats were investigated to clarify the underlying mechanism of chronic functional visceral pain,which may provide new thoughts for clinical prevention and treatment.Methods(1)IBS like rats were established by neonatal maternal separation(NMS)for 3 h daily during post-natal days 3-21 and each one was put in cubicles separately.The control rats were treated like IBS rats except NMS.The visceral hypersensitivity was assessed by recording the responses of the external oblique abdominal muscle to 40 and 60 mm Hg colorectal distention(CRD)when the rats were adult(8 weeks).(2)The levels of hippocampal NSF were detected by the method of Western blot.(3)The expression and distribution of NSF in hippocampal CA1 region were investigated by immunohistochemical technique.(4)The effects of NSF on visceral hypersensitivity were examined by the electromyogram(EMG)after the bilateral intrahippocampal injections of pep2m(a NSF specific inhibitor).(5)The expression of Glu R2(one of AMPARs subtype)were tested by Western blot after the hippocampal slices were perfused with pep2 m for 60 minutes.(6)The expression of NSF were detected by Western blot after the hippocampal slices were perfused with ZIP(a specific PKMζ inhibitor)for 30 minutes.Results(1)The sensitivity of visceral pain significantly increased in rats with IBS compared with controls(p < 0.05).(2)The expressions of hippocampal NSF significantly increased in IBS like rats compared with control rats(p < 0.05).(3)The immunohistochemical results show that NSF in hippocampal CA1 region were mainly expressed in the cells membrane and cytoplasm of small,medium-sized neurons and glial.(4)Bilateral intrahippocampal injections of pep2 m dose-dependently attenuate the visceral hypersensitivity in IBS like rats.(5)After the hippocampus slices were perfused with pep2 m,the expression of Glu R2 decreased significantly in IBS like rats(p < 0.05),but there were no obvious change in control rats.(6)After the hippocampus slices were perfused by ZIP,the expression of NSF in rats with IBS decreased significantly(p < 0.05),but there were no obvious change in control rats.Conclusion Neonatal maternal separation could lead to visceral hypersensitivity when they grown up.The underlying mechanism could be that p-PKM zeta enhanced the functions of NSF therefore increasing AMPARs-Glu R2 in the postsynaptic membrane,which facilitated the synaptic transmiss eventually inducing chronic functional visceral hypersensitivity.