%0 Journal Article %J Behav Brain Res %D 2021 %T Decreased dendritic spine density in posterodorsal medial amygdala neurons of proactive coping rats. %A Anilkumar, Shobha %A Patel, Deepika %A de Boer, Sietse F %A Chattarji, Sumantra %A Buwalda, Bauke %X

There are large individual differences in the way animals, including humans, behaviorally and physiologically cope with environmental challenges and opportunities. Rodents with either a proactive or reactive coping style not only differ in their capacity to adapt successfully to environmental conditions, but also have a differential susceptibility to develop stress-related (psycho)pathologies when coping fails. In this study, we explored if there are structural neuronal differences in spine density in brain regions important for the regulation of stress coping styles. For this, the individual coping styles of wild-type Groningen (WTG) rats were determined using their level of offensive aggressiveness assessed in the resident-intruder paradigm. Subsequently, brains from proactive (high-aggressive) and reactive (low-aggressive) rats were Golgi-cox stained for spine quantification. The results reveal that dendritic spine densities in the dorsal hippocampal CA1 region and basolateral amygdala are similar in rats with proactive and reactive coping styles. Interestingly, however, dendritic spine density in the medial amygdala (MeA) is strikingly reduced in the proactive coping rats. This brain region is reported to be strongly involved in rivalry aggression which is the criterion by which the coping styles in our study are dissociated. The possibility that structural differences in spine density in the MeA are involved in other behavioral traits of distinct coping styles needs further investigation.

%B Behav Brain Res %V 397 %P 112940 %8 2021 Jan 15 %G eng %R 10.1016/j.bbr.2020.112940 %0 Journal Article %J Behav Brain Res %D 2021 %T Repeated victorious and defeat experiences induce similar apical dendritic spine remodeling in CA1 hippocampus of rats. %A Patel, Deepika %A Anilkumar, Shobha %A Chattarji, Sumantra %A de Boer, Sietse F %A Buwalda, Bauke %X

In this study, apical dendritic spine density of neurons in hippocampal, amygdalar and prefrontal cortical areas was compared in rats that were repeatedly winning or losing social conflicts. Territorial male wild-type Groningen (WTG) rats were allowed multiple daily attacks (>20 times) on intruder males in the resident-intruder paradigm. Frequent winning experiences are known to facilitate uncontrolled aggressive behavior reflected in aggressive attacks on anesthetized males which was also observed in the winners in this study. Both winners and losers were socially housed during the experiments; winners with females to stimulate territorial behavior, and losers with two other losing male rats. Twenty-four hours after the last social encounter, brains from experienced residential winners and repeatedly defeated intruder rats were collected and neuronal morphology in selected brain regions was studied via Golgi-Cox staining. Results indicate that spine density in the apical dendrites of the hippocampal CA1 reduced similarly in both winners and losers. In addition, winners showed increased spine densities at the proximal segments (20-30 μm) of the basolateral amygdala neurons and losers tended to show a decreased spine density at the more proximal segments of the infralimbic region of prefrontal cortex neurons. No effect of winning and losing was observed in the medial amygdala. The atrophic effect of repeated defeats in hippocampal and prefrontal regions was anticipated despite the fact that social housing of the repeatedly losing intruder males may have played a protective role. The reduction of hippocampal spine density in the winners seems surprising but supports previous findings in hierarchical dominant males in rat colonies. The dominants showed even greater shrinkage of the apical dendritic arbors of hippocampal CA3 pyramidal neurons compared to the stressed subordinates.

%B Behav Brain Res %V 406 %P 113243 %8 2021 May 21 %G eng %R 10.1016/j.bbr.2021.113243 %0 Journal Article %J Behav Brain Res %D 2019 %T Rodent models of social stress and neuronal plasticity: Relevance to depressive-like disorders. %A Patel, Deepika %A Kas, Martien J %A Chattarji, Sumantra %A Buwalda, Bauke %X

Exposure to severe or persistent social stress may lead to the development of psychiatric disorders such as anxiety and depression. These mood disorders are associated with structural alterations of neural architecture in limbic brain regions that control emotion, mood and cognition. Structural remodeling may either be a sign of successful adaptation, or of failure to do so. In neuropsychiatric disorders like depression structural remodeling involves apoptosis, reduced neurogenesis, and structural remodeling of neuronal dendrites which most likely reflects the latter. Here we review key findings from animal models of psychosocial stress that have been used to gain insights into the relation between stress-related behavioral disorders like depression and structural plasticity. Specifically, we focus on models having a high face validity like social defeat stress in the resident-intruder paradigm and chronic stress of social subordination in social housing conditions. Moderate to severe social stress appears to stimulate plasticity and neuronal growth in regions of the amygdala, whereas the effects in the hippocampus and prefrontal cortex tend to be opposite. A major focus of the current review is to characterize social stress induced structural changes in these brain regions, aiming to provide insight in pathways and factors that underlie behavioral effects of stress and depression.

%B Behav Brain Res %V 369 %P 111900 %8 2019 Sep 02 %G eng %R 10.1016/j.bbr.2019.111900