Effects of Chronic Neurogenic Stress on Behavior of Rats and Contents of Sphingolipids in Their Brain and Peripheral Tissues

We studied the contents of ceramide and sphingomyelin (SM) in the hippocampus, neocortex, and peripheral tissues of rats and the behavior characteristics of these animals in the open field at different times after the induction of chronic neurogenic stress. The experiments were carried out on young Wistar rats weighing 180-220 g, with a mean level of behavioral mobility. Within the poststress period, animals demonstrated significant suppression of manifestations of motor and orientational/research activities, and intensification of autonomic manifestations of fear and anxiety (with a delay of leaving the field center). One day after termination of stressing, the content of ceramide in the hippocampus increased against the background of a drop in the SM level, but this did not occur in the neocortex, liver, and blood serum. The contents of phosphatidylcholine and phosphatidylethanolamine in the brains of animals exposed to stress did not change. Eight days after stressing, the level of ceramide in the brain structures and blood serum was significantly higher than in the control. These data suggest that the action of chronic neurogenic stress leads to activation of metabolism of sphingolipids and intensification of production of ceramide in the brain and blood serum. Accumulation of ceramide in the serum within a remote period after termination of the action of stress can serve as a marker of the stable development of a state of emotional tension accompanied by typical signs of depression-like behavior.