Morphine induces microglia apoptosis in a μOR dependent manner.

(A) Morphine could not induce the expression of TLR9 in μOR KO microglia. μOR deficient microglia cells were treated morphine at 10 µM for 12 hr and the expression of TLR9 in mRNA levels determined by quantitative real time RT-PCR as in Fig. 1A. Wild type microglial cells were treated with 10 µM morphine with or without 20 µM naloxone pretreatment. Another group of cells were treated with 10 µM DAMGO alone for 24 hr. Apoptotic cells were examined as in Fig. 3. (B). Representative light microscopic images showed TUNEL-positive microglia (red arrow head). Magnification 200×. Results represent mean ± SD from three independent experiments. * p<0.01 compared with indicated groups. (C). Apoptotic cells were analyzed by flow cytometry. These results are representative of three independent experiments.