Investigation the effects of low and high level footshock stress on empathy in rats

Introduction and Aim It is known that stress which is everywhere in the life of a modern person, has many effects on behavior and cognitive functions. Recent studies indicate that acute stress promotes empathy related prosocial behaviors such as altruism, affiliative behavior. Many factors can affect empathy behavior, such as psychological stress and anxiety. The aims of this study are to investigate the effects of low and high intensity of acute stress and the possible neurotransmitter pathways of the stress effects on empathy. Method Thirty adult male Sprague Dawley rats were used in this study. In the study, after 14 days of habituation period, all subjects were trained to rescue the stressed cage mate using the empathy test equipment. At the end of this period all subjects were randomly divided into three groups: i) Control group, ii) 0.2mA foot shock group (low-intensity), iii) 1.6mA foot shock group (high-intensity). Immediately after the foot shocks of the rats, door opening behaviors were recorded as time. After the end of the empathy experiments, the anxiety levels of all rats were initially assessed using the open field test and the elevated plus maze test after 30 minutes. Subsequently subjects were sacrified, oxytocin and vasopressin levels in amygdala and prefrontal cortex and serum corticosterone levels were measured. Findings Low intensity stress group was quicker in opening the door compared to control groups (p<0.05). In the open field test, high intensity stress group spent more time in the center of the open field arena compared to control and low intensity stress group (p<0.001 in both). In the elevated plus maze test, high intensity stress group compared to both low intensity stress and control groups, spent more time in the open arms of elevated plus maze (p < 0.008 and p < 0.03, respectively), this period was mostly spent in the center area of the elevated plus maze equipment (compared with control p<0.0001, with low intensity stress p<0.001). Prefrontal cortex oxytocin and vasopressin levels were found to be increased in low intensity stress group (oxytocin: compared with control, p<0.05; vasopressin: compared with control and high intensity stress (p<0.0001 in both). Vasopressin level in amygdala was increased in low intensity stress group compared to control and high intensity stress (p<0.05 in both) Corticosterone level was increased in low intensity stress group compared to control (p<0.002). Strong positive correlation was found between prefrontal cortex vasopressin levels and activity in middle area of open field test (r = 0.510, p<0.05). Strong positive correlation was found between serum corticosterone levels and the activity in the middle area of elevated plus maze test (r = 0.752, p<0.0001); between prefrontal cortex vasopressin levels and the activity in the middle area of elevated plus maze test (r = 0.590, p<0.01). Result In this study, we were able to demonstrate that low intensity acute stress increased empathy behavior. Also in low intensity stress group, vasopressin levels increased in prefrontal cortex and amygdalae, oxytocin level increased in prefrontal cortex. Higher intensity acute stress was associated with a lesser degree of anxiety indicators, i.e. higher ambulation in center cells of open field arena, and in the open arms of elevated plus maze test. In addition, it was seen that decision-making capacity was affected in high intensity stress group. Further research is needed to investigate gender effects, the role of dopaminergic system and other stress related pathways in acute stress.