Background & Aims: The approach to the management of chronic pain has been empirical, primarily due to the lack of information about biological mechanisms producing pain.The early postnatal period has been suggested to be the vulnerable time for neuronal development and plasticity.We aimed to investigate the effect and underlying mechanism of neonatal insult on somatic and visceral nociception in adult rats.Methods: In this study, a total volume of 25 μL complete Freunds adjuvant (CFA) was injected into left hind paw at postnatal day (PND) 10 and a total of 150 μL of CFA was injected into these rats again at PND42.von Frey Filaments and thermal behavioral tests were used to evaluate somatic pain sensation.Abdominal withdrawal reflex (AWR)scores in responding to colorectal distention were carried out to assess visceral nociception.Western blotting was employed to measure expression level of endogenous hydrogen producing enzyme Hydrogen sulfide synthesis (CBS) and TRPV1 in dorsal root ganglion cells (DRGs)(T13-L2,L4-L6).Results: (1) Neonatal CFA injection led to visceral hypersensitivity and somatic mechanic and thermo hyperalgesia., while behavioral changes in sensitivity of somatic pain caused by adult insult lasted shorter period and failed to induce visceral pain.(2) Compared to neonatal NS treated rats, the expression levels of endogenous hydrogen producing enzyme CBS and TRPV1 in DRGs (T13-L2, L4-L6) in neonatal CFA treated group were up-regulated.(3) Visceral hypersensitivity in neonatal CFA treated rats can be reversed by AOAA injection(i.p.), an antagonist of CBS.Conclusion: Neonatal insult may alter neuronal circuits which could be mediated by CBS and TRPV1.The antagonist of CBS might be beneficial in treating painful disorders.