Astrocytic GABAB Receptors in Mouse Hippocampus Control Responses to Behavioral Challenges through Astrocytic BDNF

Major depressive disorder (MDD) is a common mood disorder that affects almost 20% of the global population. In addition, much evidence has implicated altered function of the gamma-aminobutyric acid (GABAergic) system in the pathophysiology of depression. Recent research has indicated that GABA_B receptors (GABA_BRs) are an emerging therapeutic target in the treatment of stress-related disorders such as MDD. However, which cell types with GABA_BRs are involved in this process is unknown. As hippocampal dysfunction is implicated in MDD, we knocked down GABA_BRs in the hippocampus and found that knocking down these receptors in astrocytes, but not in GABAergic or pyramidal neurons, caused a decrease in immobility in the forced swimming test (FST) without affecting other anxiety- and depression-related behaviors. We also generated astrocyte-specific GABA_BR-knockout mice and found decreased immobility in the FST in these mice. Furthermore, the conditional knockout of GABA_BRs in astrocytes selectively increased the levels of brain-derived neurotrophic factor protein in hippocampal astrocytes, which controlled the decrease in immobility in the FST. Taken together, our findings contribute to the current understanding of which cell types expressing GABA_BRs modulate antidepressant activity in the FST, and they may provide new insights into the pathological mechanisms and potential targets for the treatment of depression.

Secondary screening system for preclinical testing of human lung cancer therapies

The National Cancer Institute has instituted a primary screening system for testing new agents against cultured cancer cell lines. The purpose of this study was to determine the feasibility of using a nude rat orthotopic (organ-specific) human lung cancer model system as an in vivo secondary screen for general evaluation of new anticancer agents and therapies active against lung cancer. To make this determination, we tested whether this system allows measurement of uptake and tumoricidal activity of anticancer therapies. Tumor-bearing lungs from 53 Rowett nude rats with orthotopically implanted human large-cell undifferentiated lung carcinoma (NCI-H460) were perfused ex vivo for 1 hour with or without each of two anticancer modalities. Lungs were perfused with blood-free perfusate alone (untreated control), perfusate with 100 micrograms/mL doxorubicin (treated positive control), or perfusate with lymphokine-activated killer cells plus human recombinant interleukin-2 (LAK/rIL-2). Weight gain during perfusion was the criterion used to quantitate lung injury. Treatment efficacy was measured by clonogenic assay after enzymatic disaggregation of the perfused tumors. Doxorubicin levels in the tumor and in the uninvolved lung were measured by high-performance liquid chromatography. Both treatment groups showed only slight increases in lung weight compared with that in the untreated control group, suggesting good lung tolerance of the procedure. Lung and tumor levels of doxorubicin were 320 +/- 21 ng/mg of tissue and 32 +/- 5 ng/mg of tissue (means +/- SE), respectively. Clonogenic assay demonstrated a fivefold to 10-fold reduction in the surviving fraction of tumor cells with doxorubicin but no change with LAK/rIL-2.(ABSTRACT TRUNCATED AT 250 WORDS)