BACKGROUND: Endothelin(ET) -1 is a peptide with potent actions on blood vessels and nerve system. Its expression increases in the central nervous system(CNS) in a variety of pathological conditions, inducing harmful effects on the nervous tissue. However it is not clearly elucidated whether the over-expressed ET-1 can directly induce neuronal apoptosis.OBJECTIVE: To investigate whether ET-1 can directly induce apoptosis in primarily cultured brain neurons of rat, and which ET receptor subtype(s) is involved in this action.DESIGN: Completely randomized and controlled experimental study based on cells.SETTING: Neurological department in a university hospital, pathological department of a university and laboratory center of tissue transplantation and immunology, life science and technology college.MATERIALS: This study was completed in the Pathology Department, the Institute of Tissue Transplantation and Immunology, the Life Science and Technology College of Jinan University. The subjects were primarily-cultured neurons obtained from cerebral cortex of newborn rats that were provided by the Experimental Animal Center of the Medical College, Sun Yat-sen University.INTERVENTIONS: After culturing for five days, the neurons were treated with ET-1 (0. 2 nmol/L and 20 nmol/L) for 24 hours. Apoptotic neurons were semi-quantitatively measured with Annexin V and Hoechst 33258 staining respectively. ET-1(20 nmol/L), with BQ123(a selective antagonist for ET receptor A, 1 mmol/L) or with BQ788(a selective antagonist for ET receptor B, 1 mmol/L), was added respectively into the cultures simultaneously. And the apoptotic neurons were quantitatively measured with flow cytometry 24 hours later. Equal amount of PBS, instead of ET-1, waw added into the control subjects.MAIN OUTCOME MEASURES: The effect of ET-1 on apoptosis rate of cultured rat cortical neurons, and the ET receptor subtypes involved in this action.RESULTS: Twenty-four hours after treated with 0.2 nmol/L ET-1, the Annexin-V, and Hoechest 33258 positive stained cell rates[ (23.00 ± 9.96)%,(9.82 ±0.95)% ] were of no difference as compared with those of the controls[ (13.50 ± 3.35)%, (8.21 ± 2. 17)% ]. By contrast, after incubation with the higher dose of ET-1 (20 nmol/L), significant higher rate of apoptosis was measured in Annexin V staining[(50.50 ± 10.78)%, P=0.01, n=4] and Hoechest 33258 staining[(13.78±1.52)%, P= 0. 000, n = 8] . Analyzed with flow cytometry, the apoptosis rate was (0.20±0. 15)% in the control group, (26. 11 ±3.28)% in 20 nmol/LET-1 group, and(13.58 ±4. 92)% in BQ123 +ET-1 and(9.99 ±3.30)% in BQ788 +ET-1 respectively, indicating that BQ123 and BQ788 partially-blocked the apoptosis effect of ET-1 on. cultured neurons(BQ123 + ET-1 vs ET-1, P = 0. 005; BQ788 + ET-1 vs ET-1, P = 0. 001, n = 4, respectively).CONCLUSION: The higher dose of ET-1 (20 nmol/L) can directly induce apoptosis of primarily-cultured cerebral neurons of rats. The effect of ET-1 inducing neuronal apoptosis may be mediated via both ET receptors A and B.