Serotonin and dopamine protect cells from hypothermia/rewarming cell death through an intracellular action.

Cells subjected to hypothermia (black bars) were incubated at 3°C for 24 h, followed by rewarming to 37°C for 3 h, and compared to non-cooled control cells (37°C, gray bars). Cell survival was assessed by adding MTS to the cells upon rewarming and spectrophotometrical formazon measurement. (A) DDT-1 cells show natural resistance to hypothermia, which is abrogated by the serotonin transporter (SERT) inhibitor fluoxetine (Fluox, 1 µM, 15 min) and pretreatment with the tryptophan hydroxylase inhibitor parachlorophenylalanine (PCPA, 24 h). (B to C) Concentration-dependent inhibition of hypothermic cells death by serotonin (B) and dopamine (C) in SMAC. (D) The protective effect of serotonin (30 µM, 15 min) and dopamine (20 µM, 15 min) pretreatment on hypothermic cell death is precluded by inhibition of their respective transporters with fluoxetine (1 µM, 15 min) and vanoxerine (1 µM, 15 min), but unaffected by non-specific receptor antagonists ketanserin (1 µM, 15 min) and spiperone (1 µM, 15 min). (E) Serotonin (30 µM, 15 min) and dopamine (20 µM, 15 min) pretreatment prevent caspase3/7 activation induced by hypothermia in SMAC cells, which is precluded by inhibition of their uptake by fluoxetine (1 µM, 15 min) and vanoxerine (1 µM, 15 min). ANOVA tests, different from non-cooled cells (37°C) P<0.05 (*); different from untreated hypothermic cells (Con) P<0.05 (#). Experiments consist of n≥4. Means ± SEM.