Protective effect of HCN2-induced SON sensitization on chronic visceral hypersensitivity in neonatal-CRD rat model.

Abnormal brain-gut interactions contribute to the development of chronic visceral hypersensitivity (CVH), which is the pivotal feature of irritable bowel syndrome (IBS). Despite the consensus with respect to the vital role of hyperpolarization-activated cyclic nucleotide-gated 2 (HCN2) channels in promoting painful symptoms in the peripheral nervous system, we identified that the upregulation of HCN2 in supraoptic nucleus (SON) was involved in the modulation of CVH in rat model of neonatal colorectal distention (n-CRD). Specifically, colorectal distention (CRD) upregulated the expression of c-Fos in SON in adult CVH rats, indicating the involvement of SON sensitazation in visceral sensation. Moreover, the administration of ZD7288 (the pan-HCN channel inhibitor) rather than 8-Br-cAMP (the non-specific HCN channel agonist) aggravated the CVH symptoms and reduced the phosphorylation level of CaMKII-CREB cascade. Together, the findings indicated that the upregulation of supraoptic HCN2 contributed to the sensitization of SON, which had protective effects on the modulation of CVH with the involvement of CaMKII-CREB cascade in n-CRD rat model.