“…After‐weaning models have many possibilities from a single isolation (Pournajafi‐Nazarloo et al, ; Powell et al, ), to several days or weeks. The main observed effect is anxiety, but there are reductions in neuronal activity measured through Fos expression (Lukkes et al, ; Wall et al, ; Ahern et al, ), dendritic growth (Silva‐Gómez et al, ), electrical activity, and neurotransmitters release (Cinini et al, ; Soga et al, ; Sargin et al, ; Murínová et al, ). However, some neurotransmitters can increase its release (Yorgason et al, ).…”
“…After‐weaning models have many possibilities from a single isolation (Pournajafi‐Nazarloo et al, ; Powell et al, ), to several days or weeks. The main observed effect is anxiety, but there are reductions in neuronal activity measured through Fos expression (Lukkes et al, ; Wall et al, ; Ahern et al, ), dendritic growth (Silva‐Gómez et al, ), electrical activity, and neurotransmitters release (Cinini et al, ; Soga et al, ; Sargin et al, ; Murínová et al, ). However, some neurotransmitters can increase its release (Yorgason et al, ).…”
“…Immunolabeled cells were counted by centering a counting frame within each subregion at 10x then shifting to a 40x objective; cell counts were performed within the 22,406 μm 2 counting frame in real-time throughout the z plane as previously reported [33]. Cell counts were performed in the anterior cingulate (AC), prelimbic (PL), and infralimbic (IL) subregions of the mPFC.…”
Post-weaning social isolation (PSI) has been shown to increase aggressive behavior and alter medial prefrontal cortex (mPFC) function in social species such as rats. Here we developed a novel escapable social interaction test (ESIT) allowing for the quantification of escape and social behaviors in addition to mPFC activation in response to an aggressive or nonaggressive stimulus rat. Male rats were exposed to 3 weeks of PSI (ISO) or group (GRP) housing, and exposed to 3 trials, with either no trial, all trials, or the last trial only with a stimulus rat. Analysis of social behaviors indicated that ISO rats spent less time in the escape chamber and more time engaged in social interaction, aggressive grooming, and boxing than did GRP rats. Interestingly, during the third trial all rats engaged in more of the quantified social behaviors and spent less time escaping in response to aggressive but not nonaggressive stimulus rats. Rats exposed to nonaggressive stimulus rats on the third trial had greater c-fos and ARC immunoreactivity in the mPFC than those exposed to an aggressive stimulus rat. Conversely, a social encounter produced an increase in large PSD-95 punctae in the mPFC independently of trial number, but only in ISO rats exposed to an aggressive stimulus rat. The results presented here demonstrate that PSI increases interaction time and aggressive behaviors during escapable social interaction, and that the aggressiveness of the stimulus rat in a social encounter is an important component of behavioral and neural outcomes for both isolation and group-reared rats.
“…Rats were used for experiments after 4-5 weeks (P50-60 postadolescents), or at intermediate time points, as described below. Several studies indicate that social behavior in males may be more sensitive to postweaning social isolation (Ferdman et al, 2007;Wall et al, 2012;Ahern et al, 2016). Therefore, males were the focus of the current study.…”
Children exposed to neglect or social deprivation are at heightened risk for psychiatric disorders and abnormal social patterns as adults. There is also evidence that prepubertal neglect in children causes abnormal metabolic activity in several brain regions, including the amygdala area. The medial nucleus of the amygdala (MeA) is a key region for performance of social behaviors and still undergoes maturation during the periadolescent period. As such, the normal development of this region may be disrupted by social deprivation. In rodents, postweaning social isolation causes a range of deficits in sexual and agonistic behaviors that normally rely on the posterior MeA (MeAp). However, little is known about the effects of social isolation on the function of MeA neurons. In this study, we tested whether postweaning social isolation caused abnormal activity of MeA neurons. We found that postweaning social isolation caused a decrease of in vivo firing activity of MeAp neurons, and reduced drive from excitatory afferents. In vitro electrophysiological studies found that postweaning social isolation caused a presynaptic impairment of excitatory input to the dorsal MeAp, but a progressive postsynaptic reduction of membrane excitability in the ventral MeAp. These results demonstrate discrete, subnucleus-specific effects of social deprivation on the physiology of MeAp neurons. This pathophysiology may contribute to the disruption of social behavior after developmental social deprivation, and may be a novel target to facilitate the treatment of social disorders.
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