ABSTRACT
Objective To investigate the role of mitochondrial apoptotic pathway in intrathecal doxepin?induced apoptosis in rat neurons. Methods Twenty?four adult male Wistar rats, weighing 250-300 g, in which intrathecal catheters were successfully implanted without complications, were randomly divided into 4 groups ( n=6 each) using a random number table: control group ( group C) and different concentrations of doxepin groups (D5, D10 and D20 groups). In D5, D10 and D20 groups, 5, 10, and 20 mmol∕L doxepin 0. 2 μl∕g were injected intrathecally, respectively. In group C, the equal volume of normal saline was given instead. At 6 h after intrathecal administration, the animals were sacrificed, and the lumbar segments of the spinal cords were obtained for detection of the cell apoptosis ( by TUNEL assay) , expression of Bax and Bcl?2 ( by immunohistochemistry) , release of cytochrome c ( Cyt c) , and expression of caspase?3, caspase?8 and caspase?9 mRNA ( using real?time reverse transcriptase polymerase chain reaction) . Apoptosis rate and Bcl?2∕Bax ratio were calculated. Results Compared with group C, the expression of Bax was significantly up?regulated, the expression of Bcl?2 was down?regulated, Bcl?2∕Bax ratio was decreased, the release of Cyt c and apoptosis rate were increased, and the expression of caspase?3 and caspase?9 mRNA was up?regulated in D10 and D20 groups, the expression of Bcl?2 was down?regulated in group D20 ( P0.05). The expression of Bax was significantly up?regulated, Bcl?2∕Bax ratio was decreased, the release of Cyt c and apoptosis rate were increased, and the expression of caspase?3 and caspase?9 mRNA was up?regulated in D10 and D20 groups, and the expression of Bcl?2 was down?regulated in group D20 as compared with group D5 ( P0.05) . Conclusion Mitochondrial apoptotic pathways, but not death receptor pathway, is involved in intrathecal doxepin?induced apoptosis in rat neurons.