Acute Stress Promotes Aggressive-Like Behavior in Rats Made Allergic to Tree Pollen.

It has been reported that allergies are associated with depression and possibly suicide in women. Aggression is an important behavioral component that predisposes depressed individuals to suicidal acts. In the present study we examined the relationship between allergies and aggression to determine a potential contribution of allergies in factors of risk for suicidal behavior. Because stress plays a critical role in the manifestation of clinical symptoms of allergies and also in suicidal behavior, we also studied the role of acute stress. Female inbred Brown Norway rats known for their susceptibility to respiratory allergies were sensitized and challenged with a mixture of tree pollen and evaluated in the resident-intruder test for detection of aggressive behaviors. They were also subjected to acute stress by sessions of inescapable forced swimming and re-evaluated in the resident intruder test. Animals made allergic to tree pollen and subjected to acute stress displayed increased aggressive-like behavior as compared with control-saline treated animals or to their own aggressive scores previous to the stress session. These results suggest that allergies and stress increases aggressive-like behavior, indicating that these conditions may be important factors promoting altered emotional reactivity with the potential to influence suicidal behavior.