@article {111038, title = {Stress Elicits Contrasting Effects on Rac1-Cofilin Signaling in the Hippocampus and Amygdala.}, journal = {Front Mol Neurosci}, volume = {15}, year = {2022}, month = {2022}, pages = {880382}, abstract = {

There is accumulating evidence for contrasting patterns of stress-induced morphological and physiological plasticity in glutamatergic synapses of the hippocampus and amygdala. The same chronic stress that leads to the formation of dendritic spines in the basolateral amygdala (BLA) of rats, leads to a loss of spines in the hippocampus. However, the molecular underpinnings of these divergent effects of stress on dendritic spines are not well understood. Since the activity of the Rho GTPase Rac1 and the actin-depolymerizing factor cofilin are known to play a pivotal role in spine morphogenesis, we investigated if alterations in this signaling pathway reflect the differential effects of stress on spine plasticity in the hippocampus and amygdala. A day after the end of chronic immobilization stress (2 h/day for 10 days), we found a reduction in the activity of Rac1, as well as its effector p21-activated kinase 1 (PAK1), in the rat hippocampus. These changes, in turn, decreased cofilin phosphorylation alongside a reduction in the levels of profilin isoforms. In striking contrast, the same chronic stress increased Rac1, PAK1 activity, cofilin phosphorylation, and profilin levels in the BLA, which is consistent with enhanced actin polymerization leading to spinogenesis in the BLA. In the hippocampus, on the other hand, the same stress caused the opposite changes, the functional consequences of which would be actin depolymerization leading to the elimination of spines. Together, these findings reveal a role for brain-region specific differences in the dysregulation of Rac1-to-cofilin signaling in the effects of repeated stress on two brain areas that are implicated in the emotional and cognitive symptoms of stress-related psychiatric disorders.

}, issn = {1662-5099}, doi = {10.3389/fnmol.2022.880382}, author = {Bose, Mihika and Nawaz, Mohammad Sarfaraz and Pal, Rakhi and Chattarji, Sumantra} } @article {100749, title = {Correction of amygdalar dysfunction in a rat model of fragile X syndrome}, journal = {Cell Reports}, volume = {37}, year = {2021}, month = {10/2021}, pages = {109805}, chapter = {2}, abstract = {

Fragile X syndrome (FXS), a commonly inherited form of autism and intellectual disability, is associated with emotional symptoms that implicate dysfunction of the amygdala. However, current understanding of the pathogenesis of the disease is based primarily on studies in the hippocampus and neocortex, where FXS defects have been corrected by inhibiting group I metabotropic glutamate receptors (mGluRs). Here, we observe that activation, rather than inhibition, of mGluRs in the basolateral amygdala reverses impairments in a rat model of FXS. FXS rats exhibit deficient recall of auditory conditioned fear, which is accompanied by a range of in\ vitro and in\ vivo deficits in synaptic transmission and plasticity. We find presynaptic mGluR5 in the amygdala, activation of which reverses deficient synaptic transmission and plasticity, thereby restoring normal fear learning in FXS rats. This highlights the importance of modifying the prevailing mGluR-based framework for therapeutic strategies to include circuit-specific differences in FXS pathophysiology.

}, doi = {10.1016/j.celrep.2021.109805}, author = {Fernandes, Giselle and Mishra, Pradeep K. and Nawaz, Mohammad Sarfaraz and Donlin-Asp, Paul G. and Rahman, Mohammed Mostafizur and Hazra, Anupam and Kedia, Sonal and Kayenaat, Aiman and Songara, Dheeraj and Wyllie, David J A and Schuman, Erin M. and Kind, Peter C and Chattarji, Sumantra} }