Effects of post-weaning social isolation on social behaviors and oxytocinergic activity in male and female rats

Abstract

Aims Post-weaning social deprivation is known to induce behavioral and neuronal alterations associated with anxiety and stress responses in adulthood. However, the effects of social deprivation on the development of sociability are poorly understood. We examined the effects of social deprivation on subsequent social behaviors and oxytocinergic activity using socially-isolated (approximately two months post-weaning) male and female rats. Main methods The behaviors were analyzed using a social preference test and a social approach test. Immunohistochemical investigations were conducted in the paraventricular nucleus (PVN) and supraoptic nucleus (SON) to examine the effects of social isolation on oxytocinergic activity in these regions. Oxytocinergic activity was measured by quantifying the number of oxytocin neurons expressing Fos following exposure to a novel conspecific. In all of the experiments of this study, ovariectomized females were used for social stimuli. Key findings The behavioral results show that isolation-reared females, but not males, displayed impaired social preference and decreased social approach towards ovariectomized females, compared with the pair-reared group, suggesting low priority of processing social versus non-social stimuli and low motivation for contact with a stranger, respectively. The immunohistochemical results show that social isolation decreased both the number and the ratio of Fos-positive cells in oxytocin neurons in the PVN in females, but not in males, following exposure to ovariectomized females. In the SON, the Fos-positive ratio was decreased in isolation-reared females, but not in males, compared with the pair-reared group. Significance Post-weaning social isolation changed social behaviors and oxytocinergic activity in female rats, suggesting that in female rats post-weaning social experiences contribute to the development of sociability. These findings could impact the treatment of social dysfunction in humans.

Fenofibrate ameliorates olanzapine’s side effects without altering its central effect: emphasis on FGF-21–adiponectin axis

“…Interestingly, fenofibrate alone had the ability to improve anxiety and hyperlocomotion induced by isolation without showing any sedative effect compared to olanzapine-treated rats. An important negative symptom of schizophrenia is social withdrawal, postweaning social isolation revealed a significant decrease in the Sociability index in accordance with previous outcomes (Tanaka et al ., 2019). Treatment of isolated reared rats with olanzapine significantly reversed the model-induced social withdrawal, as shown by significant increase in Sociability index.…”

Social Isolation Induces Changes in the Monoaminergic Signalling in the Rat Medial Prefrontal Cortex

“…Furthermore, the isolated animals also showed no difference between the time spent with the novel and familiar conspecific in the social novelty discrimination test, suggesting impaired social recognition. Thus, the performance of isolated rats in these tests was impaired, similar to the results found in previous studies following both longer [ 66 , 67 ] but also shorter social isolation [ 68 , 69 ]. In turn, previously isolated animals demonstrated an increased amount of affiliative behaviour when they were allowed to freely interact with a conspecific.…”

Cardiovascular protective properties of oxytocin against COVID-19

“…While these measures are effective in reducing COVID-19 morbidity, they also raise concerns for massive social isolation and long-term psychological effects [ 160 ] that decrease immunological defense [ 50 , 51 ] and thus can increase COVID-19 susceptibility. It is known that social isolation can cause CV complications [ 161 ] while disrupting normal OXT secretion [ [162] , [163] , [164] ]. Importantly, application of OXT can alleviate social isolation-induced atherosclerosis and adipose tissue inflammation [ 165 ].…”