Neonatal Maternal Deprivation Followed By Adult Stress Induces The Visceral Hypersensitivity Through The Activation Of Adrenergic Signaling

Backgrounds and aims:The pathophysiological mechanism of visceral pain in patients with irritable bowel syndrome(IBS)remains unclear,while a series of studies have shown that neonatal stresses increase the risk of visceral hyperalgesia in IBS.Previous studies have shown that neonatal maternal deprivation(NMD)did not produce visceral hyperalgesia at the age of 6 weeks.However,it is not clear whether NMD followed by adult stresses could induce visceral hyperalgesia.The aim of this study was to determine whether NMD followed by adult stress(AS)at the age of 6 weeks produce visceral pain and to investigate the roles of adrenergic signaling and P2X3 receptor in NMD plus AS-induced chronic visceral hypersensitivityMethods:1.Chronic visceral pain was established by neonatal maternal deprivation(NMD)and adult multiple stresses(AMS).2.Visceral hypersensitivity was measured by visual observation of the abdominal withdrawal reflex(AWR)and colorectal distension threshold(CRD).3.Plasma levels of norepinephrine(NE)were measured using ELISA Kit.4.Western blotting,Real-time qPCR and immunofluorescence were employed to detect the molecular expression and location5.Neuronal excitability and ATP current were recorded by whole-cell patch clamp techniques.6.Calcium imaging was used to detect the effect of NE on ATP-induced calcium signal.Results:1.NMD rats exhibited visceral hypersensitivity 6 and 24 hours after termination of AMS while age-matched control rats did not display any visceral hypersensitivity following AMS.Results of whole-cell patch clamping showed that neuronal excitability of dorsal root ganglions(DRGs)isolated from NMD+AMS rats was significantly enhanced when compared with CON+AMS rats.2.NE concentration was greatly enhanced in NMD?AAMS rats and the expressions of ?2 adrenergic receptors at protein and mRNA levels were renarkably upregulated in NMD+AMS rats.Inhibition of ?2 adrenergic receptors by butoxamine markedly enhanced the CRD threshold in a time-dependent fashion and partly reversed the neuronal hyperexcitability of T13-L2 DRGs in NMD+AMS rats.3.NMD+AMS significantly increased the protein expression of P2X3 receptor and ATP current density.P2X3 receptor antagonist A317491 significantly reversed visceral hyperalgesia of NMD+AMS rats.4.?2-AR and P2X3R were found to co-locate in colon-related DRGs neurons,and?2 receptor antagonist(BUTO)significantly reversed the expression of P2X3 receptor and the ATP current density of colon-related DRGs neurons in NMD+AMS rats.5.NE significantly increased the ATP-induced calcium signal of colon-related DRGs neurons in the control group.Conclusion:Overall,our data demonstrate that NMD plus AMS induces the occurrence of visceral hypersensitivity of rats,partly due to the enhanced NE-?2 adrenergic signaling and the up-regulation of P2X3 receptor in the primary sensory neurons.This study might shed new light on the pathogenesis of visceral hypersensitivity induced by environmental stress during the early life and adult period.