[A multicenter study on childhood Hodgkin lymphoma treated with HL-2013 regimen in China].

Objective: To evaluate the efficacy of the Hodgkin lymphoma (HL)-2013 regimen in the treatment of children with HL, and to investigate the prognostic factors of childhood HL. Methods: Clinical data of 145 children (aged ≤18 years) with newly diagnosed HL, treated with HL-2013 regimen in 8 tertiary referral centers for childhood cancer from August 2011 to April 2021 were analyzed retrospectively. All the diagnosis were confirmed by histopathological morphology and immunohistochemical examination. The clinical characteristics and treatment outcomes were summarized, and the patients were divided into different groups according to clinical characteristics. Kaplan-Meier method was used for survival analysis, and the comparison of survival rates between groups was performed with Log-rank test. Results: Of the 145 cases, there were 115 males and 30 females, the age at diagnosis was 7.9 (5.8, 10.6) years. Cervical lymph node enlargement (114 cases, 78.6%) was the common symptom of the disease, and 57 patients (39.3%) were accompanied by large masses. The most common pathological classification was mixed cell type (93 cases, 64.1%). According to the Ann Arbor staging system, there were 9 cases of stage Ⅰ, 62 cases of stage Ⅱ, 45 cases of stage Ⅲ, 29 cases of stage Ⅳ. According to the risk stratification: there were 14 cases of low-risk group, 76 cases of medium-risk group and 55 cases of high-risk group. Of all patients, 68 cases (46.9%) achieved an early complete remission (CR) after 2 courses of chemotherapy, and the CR rate was 93.8% (136/145) after first-line treatment. Disease recurrence or progression occurred in 22 cases (15.2%). Of all patients, 125 cases survived, 6 cases died and 14 cases were lost to follow-up. Among the survived cases, 123 cases were continuously at CR state,and the follow-up time was 55 (40, 76) months. The 5-year overall survival (OS) and event free survival (EFS) rates were (95.3±1.9)% and (84.2±3.0)% for the entire group, respectively. 5-year OS and EFS rates for patients with stage Ⅲ-Ⅳ were both lower than those for patients with stage Ⅰ-Ⅱ (χ2=6.28 and 7.58, both P<0.05), the 5-year OS and EFS rates for patients in high-risk group were both lower than those for patients in low-risk and medium-risk group (χ2=10.93, 7.79, both P<0.05). The 5-year OS rates for the patient with early CR and without early CR were 100.0% and (90.9±3.6)% (χ2=5.77, P=0.016). EFS rates for the patient with early CR (68 cases) and without early CR (77 cases) were (93.8±3.0)% and (75.8±5.0)% (χ2=8.78, P=0.003). Conclusions: HL-2013 regimen is significantly effective in the treatment of pediatric HL. However, the patients in high-risk group and those without early CR are prone to disease recurrence or progression. Stage Ⅲ-Ⅳ and without early CR were associated with worse prognosis.

[Multicenter clinical study on the diagnosis and treatment of childhood renal tumor].

Objective: To summarize the effect of Chinese Children's Cancer Group (CCCG) Wilms tumor (WT)-2015 protocol. Methods: This was a prospective study. CCCG-WT-2015 protocol was revised on the basis of the CCCG-WT-2009 protocol. Clinical data of 288 children diagnosed with newly diagnosed kidney neoplasms in fourteen pediatric centers between September 2015 to December 2018 were summarized. The age of onset, distribution of pathological subtypes, staging, curative effect and prognostic factors of these children were analyzed. Kaplan-Meier method was used for survival curve and Log-Rank method was used for univariate analysis. Results: Among 288 cases with kidney neoplasms, there were 261 cases of WT, including 254 cases (97.3%) with favorable histology (FH) WT and 7 cases (2.7%) with unfavorable histology WT (UFHWT). The 3 year events free survival (EFS) rate for FHWT and UFHWT were (88.9±2.1)% and (80.0±17.9)%, which were better than that in WT-2009 (81.2% and 71.7%). In the 96 cases of stage Ⅲ/Ⅳ FHWT with indications for radiotherapy, 76 cases received radiation, another 20 cases received M protocol chemotherapy (cyclophosphamide, etoposide, gentamycin, vincristine and adriamycin) instead of radiation. The 3 year EFS rate for these two groups were (84.7±4.3)% and (84.7±8.1)%(χ2=0.015, P=0.902). There were 22 renal clear cell sarcoma and 5 malignant rhabdoid tumor, 3 year EFS rate of them was (94.4±5.4)% and (20.0±17.9)%. Univariate analysis was performed for age, gender, pathological type, stage, whether rupture occurred during operation, whether complete remission (CR) occurred at the end of treatment and radiotherapy. Pathological types (χ2=44.329,P<0.01) and failure to achieve CR at the end of the treatment (χ2=49.459,P<0.01) were independent factor for predicting survival. Conclusion: Compared with CCCG-WT-2009, treatment of renal tumors in CCCG-WT-2015 study yielded good survival outcome, which can be further applied.

[Clinical analysis of 14 cases with childhood acute lymphoblastic leukemia complicated with tropical candidemia].

Objective: To investigate the clinical feature, diagnosis, treatment and prognosis of childhood acute lymphoblastic leukemia (ALL) complicated with candida tropicalis bloodstream infection (CTBI), so as to improve the understanding of this disease. Methods: The general information, clinical manifestation, auxiliary examination, treatment and outcome of 14 childhood ALL who were diagnosed with tropical candidemia between January 2015 and December 2018 in 6 hospitals were analyzed retrospectively. Clinical data of non invasive fungal disease (IFD) ALL (28 cases) and other IFD children (9 cases) admitted in the same period were collected as control group. Logistic regression model was used to analyze the risk factor of CTBI. Results: Among 14 cases, there were 7 males and 7 females, with the age ranged from 17 months to 13 years. All the cases had fever, 9 cases had digestive system symptoms and stool fungal culture were positive in 3 of them; 7 cases had respiratory system symptoms and sputum fungal culture was positive in 1 of them; 2 cases had central nervous system symptoms and 10 cases progressed into septic shock. All 14 cases had neutropenia and the neutropenia duration was 1 to 53 days. Among 14 cases, the C-reactive protein was>50 mg/L in 8 cases, in which the proportion was significantly higher than that in other invasive fungal disease(IFD) (8/14 vs. 1/9, P<0.05), meanwhile the 1, 3-ß-D-glucan detection, galactomannan detection and pulmonary imaging were not remarkable in all 14 cases. The blood culture results of 14 cases were all candida tropicalis, among which 13 cases finished drug susceptibility tests, the isolates of all cases were sensitive to flucytosine and amphotericin B, and the isolates of 4 cases were sensitive to fluconazole, voriconazole and itraconazole. Among 14 cases, 1 case lost to follow-up after giving up treatment, 1 case died before antifungal therapy and the remaining 12 cases received antifungal therapy; 7 of the 14 cases died. Univariate analysis showed that between ALL with CTBI group (14 cases) and ALL without invasive fungal disease (IFD) group (28 cases), the differences in variables such as ALL not in remission (χ²=37.847, P<0.01), length of hospital stay>15 days (χ2=8.351, P=0.004), neutropenia (χ²=14.280, P<0.01), neutropenia duration>10 days (χ²=10.254, P=0.001), use of broad-spectrum antibiotics (χ²=13.888, P<0.01), skin and mucous membrane damage (χ²= 5.923, P=0.015) were statistically significant. Conclusions: In childhood ALL complicated with tropical candidemia, the drug resistance rate and mortality rate were high. For azole-resistant tropical candida, amphotericin B liposome or echinocandins(caspofungin) -fluorocytosine combined therapy was recommended to reduce treatment-related deaths.

[Clinical analysis of 31 cases of 2019 novel coronavirus infection in children from six provinces (autonomous region) of northern China].

Objective: To analyze the epidemiological history, clinical manifestations, treatment and the short-term prognosis of 31 cases of 2019 novel coronavirus (2019-nCoV) infection in children from six provinces (autonomous region) in northern China. Methods: A retrospective analysis of the epidemiological history, clinical symptoms, signs, laboratory examinations, chest imaging, treatment and the short-term prognosis of 31 cases of 2019-nCoV was conducted. The patients were diagnosed between January 25th, 2020 and February 21st, 2020 in 21 hospitals in 17 cities of six provinces (autonomous region) of Shaanxi, Gansu, Ningxia, Hebei, Henan and Shandong. Results: The age of the 31 children with 2019-nCoV infection was 7 years and 1 month (6 months-17 years). Nine cases (29%) were imported cases. Other 21 cases (68%) had contact with confirmed infected adults. One case (3%) had contact with asymptomatic returnees from Wuhan. Among the 31 children, 28 patients (90%) were family cluster cases. The clinical types were asymptomatic type in 4 cases (13%), mild type in 13 cases (42%), and common type in 14 cases (45%). No severe or critical type existed. The most common symptom was fever (n=20, 65%), including 1 case of high fever, 9 cases of moderate fever, 10 cases of low fever. Fever lasted from 1 day to 9 days. The fever of fifteen cases lasted for ≤3 d, while in other 5 cases lasted >3 d. Other symptoms included cough (n=14, 45%), fatigue (n=3, 10%) and diarrhea (n=3, 10%). Pharyngalgia, runny nose, dizziness, headache and vomiting were rare. In the early stage, the total leukocytes count in peripheral blood decreased in 2 cases (6%), the lymphocytes count decreased in 2 cases (6%), and the platelet count increased in 2 cases (6%).Elevation of C-reactive protein (10%, 3/30), erythrocyte sedimentation rate (19%, 4/21), procalcitonin (4%,1/28), liver enzyme (22%, 6/27) and muscle enzyme (15%, 4/27) occurred in different proportions. Renal function and blood glucose were normal. There were abnormal chest CT changes in 14 cases, including 9 cases with patchy ground glass opacities and nodules, mostly located in the lower lobe of both lungs near the pleural area. After receiving supportive treatment, the viral nucleic acid turned negative in 25 cases within 7-23 days. Among them, 24 children (77%) recovered and were discharged from hospital. No death occurred. Conclusions: In this case series, 2019-nCoV infection in children from six provinces (autonomous region) in northern China are mainly caused by close family contact. Clinical types are asymptomatic, mild and common types. Clinical manifestations and laboratory examination results are nonspecific. Close contact history of epidemiology, nucleic acid detection and chest imaging are important bases for diagnosis of 2019-nCoV infection. After general treatment, the short-term prognosis is good.

STAT5A reprograms fatty acid metabolism and promotes tumorigenesis of gastric cancer cells.

OBJECTIVE: The aim of this study was to determine the underlying effect of STAT5A-mediated fatty acid metabolism on the tumorigenesis of gastric cancer cells. MATERIALS AND METHODS: The expression patterns of STAT5A and FASN in gastric cancer were investigated based on the Cancer Genome Atlas (TCGA) database and compared between 40 pairs of cancer samples and adjacent tissues. The pathological significance of STAT5A in gastric cancer was explored by GESA assay, and the molecular mechanism of STAT5A-mediated FASN expression was investigated by Luciferase assay and ChIP-qPCR. Fatty acid metabolic change was explored by detecting the content of neutral lipid, triglycerides, and phospholipids in STAT5A silenced MKN28 and AGS cells. Furthermore, Cell Counting Kit-8 (CCK-8) assay, colony formation, and Mouse xenograft were used to detect the function of STAT5A-mediated fatty acid metabolism on tumorigenic ability of gastric cancer cells. RESULTS: Upregulated STAT5A in gastric cancer was found to be not only an unconventional risk for over survival of gastric cancer patients, but also associated with fatty acid metabolism signaling. Furthermore, STAT5A can regulate the expression of the fatty acid binding protein 5 (FABP5) by binding to the promoter of FABP5 in MKN28 and AGS cells. Functional studies have shown that STAT5A-dependent FABP5 expression promoted the proliferation and tumorigenesis of gastric cancer cells by reprogramming intracellular fatty acid metabolism. CONCLUSIONS: Our results indicate that STAT5A-dependent FABP5 expression plays a carcinogenic role in the tumorigenesis of gastric cancer cells via reprogramming intracellular fatty acid metabolism, which establishes a new mechanism for the tumorigenesis of gastric cancer cells.

RETRACTED: miR-1290 promotes proliferation and suppresses apoptosis in acute myeloid leukemia by targeting FOXG1/SOCS3.

Retraction statement. We, the Editors and Publisher of Journal of Biological Regulators and Homeostatic Agents, have retracted the following article: "miR-1290 promotes proliferation and suppresses apoptosis in acute myeloid leukemia by targeting FOXG1/SOCS3". Published in our Vol. 33 n. 6, 2019 issue, DOI: 10.23812/19-189-A. The article has been retracted following receipt of information from the corresponding author X.L. Ju, informing us that "they found that the cell lines they had been experimenting with were contaminated, and some of the results could not be repeated. In order not to mislead readers, they have withdrawn this manuscript with apologies". The article is withdrawn from all print and electronic editions.We have been informed in our decision-making by our policy on publishing ethics and integrity and the COPE guidelines on retractions.The retracted article will remain online to maintain the scholarly record, but it will be digitally watermarked on each page as "Retracted."

RETRACTED: miR-1290 promotes proliferation and suppresses apoptosis in acute myeloid leukemia by targeting FOXG1/SOCS3.

Retraction statement. We, the Editors and Publisher of Journal of Biological Regulators and Homeostatic Agents, have retracted the following article: "miR-1290 promotes proliferation and suppresses apoptosis in acute myeloid leukemia by targeting FOXG1/SOCS3". Published in our Vol. 33 n. 6, 2019 issue, DOI: 10.23812/19-189-A. The article has been retracted following receipt of information from the corresponding author X.L. Ju, informing us that "they found that the cell lines they had been experimenting with were contaminated, and some of the results could not be repeated. In order not to mislead readers, they have withdrawn this manuscript with apologies". The article is withdrawn from all print and electronic editions.We have been informed in our decision-making by our policy on publishing ethics and integrity and the COPE guidelines on retractions.The retracted article will remain online to maintain the scholarly record, but it will be digitally watermarked on each page as "Retracted."

[O-GlcNAc glycosylation influences the biological behaviors and etoposide-induced apoptosis of Nalm-6 cells].

Objective: To explore the effects of O-GlcNAc glycosylation and its key enzyme OGT on the biological behaviors and etoposide (Vp16) -induced apoptosis of Nalm-6 cells. Methods: Low O-GlcNAc modified Nalm-6 cells model was established with Alloxan, an inhibitor of OGT. The influence of Alloxan on Nalm-6 cells proliferation was checked by CCK-8 assay, apoptosis and cell cycle by flow cytometry. Nalm-6 cells were treated with different concentrations of Vp16 for 12 h, and then the O-GlcNAc level and the expressions of OGT were examined by Western blot. After treating Nalm-6 with Alloxan for 24 h and then 5 µg/ml of Vp16 for 12 h, the apoptosis of different groups were measured with flow cytometry, and the expression of apoptosis-associated proteins Bax and Bcl-2 were examined by Western blot. Results: With the concentration of Vp16 increasing, the O-GlcNAc modified levels of total protein and the expression of OGT were up regulated (P<0.05, n=6) ; Alloxan could slow down the proliferation capacity, induce apoptosis[ (15.190±2.539) % vs (21.910±4.105) %, P=0.007], arrest cell cycle[G1 phase: (43.534±4.453) % vs (57.322±6.091) %, P=0.003; S phase: (50.747±5.937) % vs (37.201±4.661) %, P=0.001]. Alloxan could inhibit the apoptosis caused by Vp16[ (75.195±13.845) % vs (52.741±10.815) %, P=0.011]along with Bax decreasing (5.496±1.998 vs 2.950±0.703, P=0.015) and Bcl-2 increasing (0.454±0.125 vs 0.803±0.223, P=0.013) . Conclusion: Changes of O-GlcNAc modified level of Nalm-6 cells along with the inhibition of OGT could influence the biological behaviors and inhibit apoptosis induced by Vp16.

Effect of tumor necrosis factor-induced protein 8 on T-cell-mediated immunity in mice after thermal injury.

Tumor necrosis factor-induced protein 8(TNFAIP8), the first identified member of the TNFAIP8 family, shares considerable sequence homology with members of this family. It is expressed in a wide variety of human normal tissues, with relatively higher levels in lymphoid tissues and placenta. The present study was designed to examine the effect of TNFAIP8 on T-cell-mediated immunity secondary to burn injury. Sixty male mice were randomly divided into four groups as follows: sham burn group, burn group, burn with TNFAIP8-siRNA transfection group, and burn with negative control transfection group, and they were sacrificed at designated time points. CD4+ T cells were isolated using MACS microbeads. T-Cell proliferation was analyzed with MTT assay, and IL-2, soluble IL-2R, IL-4, interferon-γ (IFN-γ) were determined with enzyme-linked immunosorbent assay kits. It was found that CD4+ T lymphocyte proliferative activity was significantly down-regulated when TNFAIP8 gene was silenced by siRNA in mice at 24 h post burn. Down-regulation of TNFAIP8 can significantly decrease expression levels of IL-2 and soluble IL-2R at 24 h after thermal injury. These results demonstrated that TNFAIP8 appeared to be involved in the immune regulation of CD4+ T lymphocytes, and the decreased expression of TNFAIP8 could affect T lymphocyte functions after thermal injury.

Downregulation of survivin by siRNA inhibits invasion and promotes apoptosis in neuroblastoma SH-SY5Y cells

Neuroblastoma is a solid tumor that occurs mainly in children. Malignant neuroblastomas have a poor prognosis because conventional chemotherapeutic agents are not very effective. Survivin, a member of the inhibitor of the apoptosis protein family, plays a significant role in cell division, inhibition of apoptosis, and promotion of cell proliferation and invasion. Previous studies found that survivin is highly expressed in some malignant neuroblastomas and is correlated with poor prognosis. The aim of this study was to investigate whether survivin could serve as a potential therapeutic target of human neuroblastoma. We employed RNA interference to reduce survivin expression in the human neuroblastoma SH-SY5Y cell line and analyzed the effect of RNA interference on cell proliferation and invasion in vitro and in vivo. RNA interference of survivin led to a significant decrease in invasiveness and proliferation and increased apoptosis in SH-SY5Y cells in vitro. RNA interference of survivin inhibited tumor growth in vivo by 68±13% (P=0.002) and increased the number of apoptotic cells by 9.8±1.2% (P=0.001) compared with negative small interfering RNA (siRNA) treatment controls. Moreover, RNA interference of survivin inhibited the formation of lung metastases by 92% (P=0.002) and reduced microvascular density by 60% (P=0.0003). Survivin siRNA resulted in significant downregulation of survivin mRNA and protein expression both in vitro and in vivo compared with negative siRNA treatment controls. RNA interference of survivin was found to be a potent inhibitor of SH-SY5Y tumor growth and metastasis formation. These results support further clinical development of RNA interference of survivin as a treatment of neuroblastoma and other cancer types.

Downregulation of survivin by siRNA inhibits invasion and promotes apoptosis in neuroblastoma SH-SY5Y cells.

Neuroblastoma is a solid tumor that occurs mainly in children. Malignant neuroblastomas have a poor prognosis because conventional chemotherapeutic agents are not very effective. Survivin, a member of the inhibitor of the apoptosis protein family, plays a significant role in cell division, inhibition of apoptosis, and promotion of cell proliferation and invasion. Previous studies found that survivin is highly expressed in some malignant neuroblastomas and is correlated with poor prognosis. The aim of this study was to investigate whether survivin could serve as a potential therapeutic target of human neuroblastoma. We employed RNA interference to reduce survivin expression in the human neuroblastoma SH-SY5Y cell line and analyzed the effect of RNA interference on cell proliferation and invasion in vitro and in vivo. RNA interference of survivin led to a significant decrease in invasiveness and proliferation and increased apoptosis in SH-SY5Y cells in vitro. RNA interference of survivin inhibited tumor growth in vivo by 68 ± 13% (P=0.002) and increased the number of apoptotic cells by 9.8 ± 1.2% (P=0.001) compared with negative small interfering RNA (siRNA) treatment controls. Moreover, RNA interference of survivin inhibited the formation of lung metastases by 92% (P=0.002) and reduced microvascular density by 60% (P=0.0003). Survivin siRNA resulted in significant downregulation of survivin mRNA and protein expression both in vitro and in vivo compared with negative siRNA treatment controls. RNA interference of survivin was found to be a potent inhibitor of SH-SY5Y tumor growth and metastasis formation. These results support further clinical development of RNA interference of survivin as a treatment of neuroblastoma and other cancer types.

Silencing of survivin using YM155 induces apoptosis and chemosensitization in neuroblastomas cells.

OBJECTIVES: Aggressive cell growth and chemoresistance are notorious obstacles in neuroblastoma therapy. Accumulating evidence suggests that survivin is preferentially expressed in cancer cells and plays a crucial role in cell division and apoptosis dysfunction. Thus, in the present study, we investigated whether silencing of survivin, using a novel small-molecule survivin suppressant, YM155 could suppress the proliferation and induce chemosensitization of neuroblastoma cells. MATERIALS AND METHODS: SH-SY5Y human neuroblastomas cells were treated with YM155 (10 to 500 mM) and/or chemotherapeutic agent cisplatin for 72 hours, and cell viability, apoptosis, mRNA and protein expression level were then evaluated. Furthermore, the efficacy of YM155 combined with cisplatin was further examined in established xenograft models. RESULTS: YM155 suppressed expression of survivin, inhibited the proliferation and induced apoptosis in SH-SY5Y cells in a concentration-dependent manner. Reduced levels of survivin sensitized SH-SY5Y to the chemotherapeutic agent cisplatin. YM155 showed antiproliferative effects and induced tumor regression and apoptosis in established SH-SY5Y xenograft models. Cisplatin showed antitumor activity against SH-SY5Y cells, it did not induce survivin upregulation. Combination treatment of YM155 and cisplatin induced a greater rate of apoptosis than the sum of the single-treatment rates and promoted tumor regression without enhanced body weight loss in the SH-SY5Y xenograft models. CONCLUSIONS: The concomitant combination of YM155 with cisplatin induced more intense apoptosis compared with each single treatment in vivo and in vitro. YM155 in combination with cisplatin is well tolerated and shows greater efficacy than either agent alone in mouse xenograft models.

Noncompetitive antagonist-binding sites of rat and housefly gamma-aminobutyric acid receptors display different enantiospecificities for tert-butyl(isopropyl)bicyclophosphorothionate.

The enantiomers of 4-tert-butyl-3-isopropyl-2,6,7-trioxa-1-phosphabicyclo[2.2.2 ]octane 1-sulfide (TBIPPS) were prepared in nine steps from diethyl tert-butylmalonate, and their abilities to compete with [3H]1-(4-ethynylphenyl)-4-n-propyl-2,6,7-trioxabicyclo[2.2.2 ]octane (EBOB), a noncompetitive antagonist of ionotropic gamma-aminobutyric acid (GABA) receptors, at their binding site were investigated using rat brain and housefly head membranes. The (S)-(-)-isomer of TBIPPS (IC50 = 398 nM) was more potent than was the (R)-(+)-isomer of TBIPPS (IC50 = 1220 nM) in rat receptors, while the potencies of (S)-TBIPPS 104 nM) and (R)-TBIPPS (IC50 = 94.4 nM) in housefly receptors were almost the same. The different enantiospecificities of rat and housefly receptors indicate that the three-dimensional structure of the binding site might be different between these receptors. In a region of the rat binding site there might be a steric bulk that interacts less favorably with (R)-TBIPPS than with (S)-TBIPPS, while in the corresponding region of the housefly binding site there might not be such a steric bulk that leads to specificity for these compounds.

5-[4-(3,3-Dimethylbutoxycarbonyl)phenyl]-4-pentynoic acid and its derivatives inhibit ionotropic gamma-aminobutyric acid receptors by binding to the 4'-ethynyl-4-n-propylbicycloorthobenzoate site.

Acyclic noncompetitive antagonists of ionotropic gamma-aminobutyric acid (GABA) receptors, bearing an ester or ether linkage, were designed, synthesized, and assayed for their inhibition of the specific binding of [3H]4'-ethynyl-4-n-propylbicycloorthobenzoate (EBOB), a radiolabeled noncompetitive antagonist, to rat brain and housefly head membranes. 5-[4-(3,3-Dimethylbutoxycarbonyl)phenyl]-4-pentynoic acid (DBCPP), a butyl benzoate analogue, was found to competitively inhibit the binding of [3H]EBOB in rat brain membranes, with an IC50 of 88 nM. The potency conferred by the p-substituent decreased in the order C(triple bond)C(CH2)2COOH > C(triple bond)C(CH2)2COOCH3 > C(triple bond) CH > Br. Pentyl phenyl ethers were equally potent compared with butyl benzoates, while phenyl pentanoates and benzyl butyl ethers were less pont. These compounds were generally less active in housefly head membranes than in rat brain membranes. The introduction of an isopropyl group into the 1-position of the 3,3-dimethylbutyl group of a butyl benzoate and two benzyl butyl ethers caused an increase in potency in housefly GABA receptors, whereas this modification at the corresponding position of other compounds led to an unchanged or decreased potency. In the case of rat receptors, this modification resulted in a decrease in potency except for a phenyl pentanoate. To confirm that DBCPP interferes with GABA receptor function, we performed whole-cell patch clamp experiments with rat dorsal root ganglion neurons in the primary culture. Repeated co-applications of GABA and DBCPP suppressed GABA-induced whole-cell currents with an IC50 of 0.54 microM and a Hill coefficient of 0.7. These findings indicate that DBCPP and its derivatives inhibit ionotropic GABA receptors by binding to the EBOB site and that there might be structural difference in the noncompetitive antagonist-binding site between rat and housefly GABA receptors.