Consequences of Social Isolation on Behavior and Hypothalamic Monoaminergic Transmission in Adult Rats of Different Social Statuses

In recent years, social isolation stress of humans and its importance in the development of behavioral disorders of psychiactic nature has become mostly current. Experimental studies using animal models have demonstrated that social stress can induce depressive- and anxiety-like behaviors, as well as neuroendocrine and physiological dysregulation. Stress-related influences are known to alter central neurotransmitter systems, particularly those involved in monoaminergic transmission. Studies have shown that intracerebral neurotransmission dysfunction such as serotonine, norepinephrine and dopamine play an important role in the development of anxiety and depression. The impact of stress varies based on individual neurophysiological characteristics, including social status. The aim of this study was to investigate the effects of stress induced by social isolation on behavior and hypothalamic monoaminergic transmission in rats of different social statuses. Experiments were performed on groups of white male laboratory rats. Dominant and submissive individuals in groups were identified using two methods based on competition for food and water. Social isolation of dominant and submissive rats was carried out for 14 days in small individual cages. Depressive and anxiety-like behaviors were evaluated using the “forced swim” and “elevated cross maze” tests.  According to behavioral tests, following social isolation, both dominant and submissive rats exhibited anxiety-like behaviors. In response to isolation, an increase in dopamine concentrations was observed in the hypothalamus of rats. Norepinephrine levels were significantly elevated only in dominant rats, who exhibited lower levels of anxiety compared to their submissive counterparts. Thus, a 14-day social isolation elicits anxiety-like behavior in both dominant and submissive individuals, which is associated with alterations in hypothalamic monoaminergic signaling, notably characterized by elevated dopamine and norepinephrine levels. These findings suggest that the observed increases in hypothalamic monoamine concentrations reflect compensatory and adaptive neurochemical responses aimed at mitigating the adverse effects of prolonged stress exposure and preventing the development of stress-related pathologies. According to the results, submissive individuals exhibit significantly greater sensitivity to social isolation stress than their dominant counterparts. These findings highlight the importance of considering individual social profiles in future research on stress adaptive mechanisms and stress-induced psychopathologies.