AIM:To determine the distribution of neurons expressingc-Fos and nitric oxide synthase(NOS)in the central nervesystem(CNS)following esophageal acid exposure,and toinvestigate the relationship between c-Fos and NOS.METHODS:Twelve Wistar rats were randomly divided intotwo equal groups.Hydrochloric acid with pepsin was perfusedin the lower part of the esophagus for 60 min.As a control,normal saline was used.Thirty minutes after the perfusion,the rats were killed and brains were removed and processedfor c-Fos immunohistochemistry and NADPH-d histochemistry.Blood pressure(BP),heart rate(HR),and respiratory rate(RR)during the experimental procedures were recordedevery 10 min.RESULTS:There were no significant differences in BP,HRand RR between the two groups,c-Fos immunoreactivitywas significantly increased in rats receiving acid plus pepsinperfusion in amygdala(AM),paraventricular nucleus(PVN),parabrachial nucleus(PBN),nucleus tractus solitarius anddorsal motor nucleus of vagus(NTS/DMV),nucleusambiguous(NA),reticular nucleus of medulla(RNM)andarea postrema(AP).NOS reactivity in this group wassignificantly increased in PVN,PBN,NTS/DMV,RNM andAP.c-Fos and NOS had significant correlation betweenPVN,PBN,NTS/DMV,RNM and AP.CONCLUSION:Acid plus pepsin perfusion of theesophagus results in neural activation in areas of CNS,and NO is likely one of the neurotransmitters in some ofthese areas. AIM: To determine the distribution of neurons expressing c-Fos and nitric oxide synthase (NOS) in the central nervous system (CNS) following esophageal acid exposure, and to investigate the relationship between c-Fos and NOS.METHODS: Twelve Wistar rats were randomly divided intotwo equal groups. Hydrochloric acid with pepsin was perfusedin the lower part of the esophagus for 60 min. As a control, normal saline was used. Thirty minutes after the perfusion, the rats were killed and brains were removed and processed for c-Fos immunohistochemistry and NADPH -d histochemistry. Blood pressure (BP), heart rate (HR), and respiratory rate (RR) during the experimental procedures were recorded de 10very.RESULTS: There were no significant differences in BP, HR and RR between the two groups, c- Fos immunoreactivity was significantly increased in rats receiving acid plus pepsin perfusion in amygdala (AM), paraventricular nucleus (PVN), parabrachial nucleus (PBN), nucleus tractus solitarius and dorsal motor nucleus of vagus (NTS / DMV), nucl eusambiguous (NA), reticular nucleus of medulla (RNM) andarea postrema (AP) .NOS reactivity in this group wassignificantly increased in PVN, PBN, NTS / DMV, RNM andAP.c- Fos and NOS had significant correlation between PVN, PBN, NTS / DMV, RNM and AP. CONCLUSION: Acid plus pepsin perfusion of the esophagus results in neural activation in areas of CNS, and NO is likely one of the neurotransmitters in some of the areas.