AIM： To assess the role of hyperpolarization-activated cyclic nucleotide-gated cation （HCN） channels in regu- lating the excitability of vagal and spinal gut afferents. METHODS： The mechanosensory response of mese...AIM： To assess the role of hyperpolarization-activated cyclic nucleotide-gated cation （HCN） channels in regu- lating the excitability of vagal and spinal gut afferents. METHODS： The mechanosensory response of mesen- teric afferent activity was measured in an ex vivo murine jejunum preparation. HCN channel activity was recorded through voltage and current clamp in acutely dissoci- ated dorsal root ganglia （DRG） and nodose ganglia （NG） neurons retrogradely labeled from the small intestine through injection of a fluorescent marker （DiI）. The isoforms of HCN channels expressed in DRG and NG neurons were examined by immunohistochemistry. RESULTS： Ramp distension of the small intestine evok- ed biphasic increases in the afferent nerve activity, re- flecting the activation of low- and high-threshold fibers.HCN blocker CsCl （5 mmol/L） preferentially inhibited the responses of low-threshold fibers to distension and showed no significant effects on the high-threshold re- sponses. The effect of CsCI was mimicked by the more selective HCN blocker ZD7288 （10 ~mol/L）. In 71.4% of DiI labeled DRG neurons （/7 = 20） and 90.9% of DiI labeled NG neurons （n = 10）, an inward current （Ih current） was evoked by hyperpolarization pulses which was fully eliminated by extracellular CsCI. In neurons expressing Ih current, a typical ＂sag＂ was observed upon injection of hyperpolarizing current pulses in cur- rent-clamp recordings. CsCI abolished the sag entirely. In some DiI labeled DRG neurons, the Ih current was potentiated by 8-Br-cAMP, which had no effect on the Ih current of DiI labeled NG neurons. Immunohistochem- istry revealed differential expression of HCN isoforms in vagal and spinal afferents, and HCN2 and HCN3 seemed to be the dominant isoform in DRG and NG, respec- tively.CONCLUSION： HCNs differentially regulate the excit- ability of vagal and spinal afferent of murine small in- testine.展开更多
基金Supported by Science and Technology Commission of Shanghai Municipality,No. 10ZR1417300Educational Commission of Shanghai Municipality,No. 10ZZ69
文摘AIM： To assess the role of hyperpolarization-activated cyclic nucleotide-gated cation （HCN） channels in regu- lating the excitability of vagal and spinal gut afferents. METHODS： The mechanosensory response of mesen- teric afferent activity was measured in an ex vivo murine jejunum preparation. HCN channel activity was recorded through voltage and current clamp in acutely dissoci- ated dorsal root ganglia （DRG） and nodose ganglia （NG） neurons retrogradely labeled from the small intestine through injection of a fluorescent marker （DiI）. The isoforms of HCN channels expressed in DRG and NG neurons were examined by immunohistochemistry. RESULTS： Ramp distension of the small intestine evok- ed biphasic increases in the afferent nerve activity, re- flecting the activation of low- and high-threshold fibers.HCN blocker CsCl （5 mmol/L） preferentially inhibited the responses of low-threshold fibers to distension and showed no significant effects on the high-threshold re- sponses. The effect of CsCI was mimicked by the more selective HCN blocker ZD7288 （10 ~mol/L）. In 71.4% of DiI labeled DRG neurons （/7 = 20） and 90.9% of DiI labeled NG neurons （n = 10）, an inward current （Ih current） was evoked by hyperpolarization pulses which was fully eliminated by extracellular CsCI. In neurons expressing Ih current, a typical ＂sag＂ was observed upon injection of hyperpolarizing current pulses in cur- rent-clamp recordings. CsCI abolished the sag entirely. In some DiI labeled DRG neurons, the Ih current was potentiated by 8-Br-cAMP, which had no effect on the Ih current of DiI labeled NG neurons. Immunohistochem- istry revealed differential expression of HCN isoforms in vagal and spinal afferents, and HCN2 and HCN3 seemed to be the dominant isoform in DRG and NG, respec- tively.CONCLUSION： HCNs differentially regulate the excit- ability of vagal and spinal afferent of murine small in- testine.
