CHRONIC UNPREDICTABLE MOVEMENT RESTRAINT STRESS DISRUPTS SOCIAL BEHAVIOUR VIA REGION-SPECIFIC SEROTONIN AND DOPAMINE ALTERATIONS IN ADULT MALE RATS

Chronic stress is a major risk factor for social dysfunction and affective disorders, yet its neurochemical substrates remain incompletely defined. Using a chronic unpredictable movement restraint (CUMR) paradigm, we examined the impact of prolonged stress on social behavior and monoaminergic signaling in adult male rats. Animals were exposed to 2, 4, or 6 hours of daily restraint for three weeks and compared with non-stressed controls. Social investigation, social interaction, and dominance behaviors were assessed, followed by quantification of synaptophysin, serotonin, dopamine, and serotonin turnover in key limbic and hypothalamic regions. CUMR exposure reduced body weight gain and significantly decreased investigation of an unfamiliar conspecific while increasing dominant behavior. Neurochemically, stressed rats showed reduced serotonin levels in the hippocampus, increased dopamine levels in the amygdala and hypothalamus, and elevated serotonin turnover in the amygdala. Correlation analyses revealed that hippocampal serotonin levels were positively associated with social behavior, whereas amygdalar serotonin levels showed a negative association. Dominant behavior was positively correlated with hypothalamic dopamine levels. These findings demonstrate that chronic unpredictable stress impairs social behaviour through region-specific alterations in serotonergic and dopaminergic systems. The data highlight distinct limbic and hypothalamic monoamine signatures underlying stress-induced social dysfunction, with relevance for stress-related neuropsychiatric disorders.