AIM:- To investigate the response of astrocytes and neurons in rat lumbo-sacral spinal cord and medulla oblongata induced by chronic colonic inflammation, and the relationship between them.METHODS: Thirty-three male Sprague-Dawley rats were randomly divided into two groups: experimental group (n = 17), colonic inflammation was induced by intra-luminal administration of trinitrobenzenesulfonic acid (TNBS);control group (n = 16), saline was administered intra-luminally.After 3, 7, 14, and 28 d of administration, the lumbo-sacral spinal cord and medulla oblongata were removed and processed for anti-glial fibrillary acidic protein (GFAP),Fos and GFAP/Fos immunohistochemistry.RESULTS: Activated astrocytes positive for GFAP were mainly distributed in the superficial laminae (laminae Ⅰ-Ⅱ)of dorsal h, intermediolateral nucleus (laminae V),posterior commissural nucleus (laminae X) and anterolateral nucleus (laminae Ⅸ). Fos-IR (Fos-immunoreactive)neurons were mainly distributed in the deeper laminae of the spinal cord (laminae Ⅲ-Ⅳ, V-Ⅵ). In the medulla oblongata, both GFAP-IR astrocytes and Fos-IR neurons were mainly distributed in the medullary visceral zone (MVZ). The density of GFAP in the spinal cord of experimental rats was significantly higher after 3, 7, and 14 d of TNBS administration compared with the controls (50.4±16.8,29.2±6.5, 24.1±5.6, P＜0.05). The density of GFAP in MVZ was significantly higher after 3 d of TNBS administration (34.3±2.5, P＜0.05). After 28 d of TNBS administration,the density of GFAP in the spinal cord and MVZ decreased and became comparable to that of the controls (18.0±4.9,14.6±6.4, P＞0.05).CONCLUSION: Astrocytes in spinal cord and medulla oblongata can be activated by colonic inflammation. The activated astrocytes are closely related to Fos-IR neurons.With the recovery of colonic inflammation, the activity of astrocytes in the spinal cord and medulla oblongata is reduced.