Abstract:Objective: To investigate the involvement of the distal cerebrospinal fluid contacting neurons(CSF-CNs) in modulation of sigmoid pain stimulation.Methods: The CB-HRP/ Fos double-labeling method was used to observe the expression of Fos in CB-HRP positive neurons following the sigmoid pain stimulation.Results: After the injection of formalin into the sigmoid wall,pain score increased remarkably,and companied by the increased expression of Fos in the CB-HRP labeled neurons.Conclusion: The distal CSF-CNs may be involved in the processing of sigmoid pain.