Rat acute toxicity (LD50) 2.8753 mol/kg

Test compounds (4-Hydroxyflavanone) were first assayed at 10 mkM for intrinsic activity using the [35S]GTP-gamma-S binding assay and CHO cell membrane homogenates that express the human muOR, deltaOR, or kappaOR. The subtype selective agonists (D-Ala2,MePhe4,Gly-ol5)enkephalin (DAMGO, muOR), (D-Pen2,D-Pen5)enkephalin (DPDPE, deltaOR), or U69,593 (kappaOR) were run as positive controls as appropriate. The CHO membranes were incubated in duplicate in 1.4 mL polypropylene tubes (Matrix Technologies, Hudson, NH) with positive control or test compound, 0.1 nM [35S]GTP-gamma-S, and 1 mkM GDP in 50 mM HEPES buffer (pH 7.4) at room temperature for 1 h, after which bound radioligand was separated from free via rapid vacuum filtration over GF-B filters with a Brandel Scientific (Gaithersburg, MD) 96-well harvester. Bound radioactivity was determined using a TopCount 12-detector instrument (Packard Instruments) using standard scintillation counting techniques. The data were normalized to samples containing vehicle (basal binding).