Bisindolylmaleimide I (BIM) is a highly selective, cell-permeable, and reversible protein kinase C (PKC) inhibitor (Ki = 14 nM) that is structurally similar to the poorly selective PKC inhibitor staurosporine. It acts as a competitive inhibitor for the ATP binding site of PKC and shows high selectivity for PKC慣-, 棺1-, 棺2-, 款-, 灌-, and 琯-isozymes.1 BIM directly inhibits GSK3 in primary adipocyte lysates (IC50 = 360 nM) and in GSK3棺 immunoprecipitates derived from rat epididymal adipocytes (IC50 = 170 nM). This compound also competitively antagonizes the 5-HT3 receptor with a Ki value of 61 nMbr>