SOCIAL INTERACTIONS IN RATS - BEHAVIORAL AND NEUROCHEMICAL ALTERATIONS IN DSP-4-TREATED RATS

Noradrenergic neurotoxin DSP-4, preceded by zimelidine to prevent sero tonin depletion, was administered IP to rats behaving in a defensive-s ubmissive manner in a resident-intruder paradigm. Computer-based ethol ogical analysis revealed the decrease of frequency and duration of def ensive episodes and marked increase of offensive aggression. This migh t suggest an increase of aggressiveness and therefore support the noti on of an inhibitory role of the noradrenergic system in aggressive beh avior independently of the model used. Dramatically changed attitude t oward the partner might also result from fear reduction or inadequate responsiveness to environmental factors because DSP-4-treated rats exp lored more than controls in stressogenic, highly illuminated area. HPL C analysis showed significant reduction of noradrenaline (NA) concentr ation in amygdala, hypothalamus, hippocampus, and frontal cortex. Simu ltaneously there occurred a considerable decrease in dopamine (DA) and serotonin (5-HT), and their metabolite levels. This suggests an atten uated activity of the DA and 5-HT systems that we consider as an effec t secondary to NA depletion, which reflects the functional interaction s between DA, 5-HT, and NA systems.