Is structural remodeling in regions governing memory an univocal correlate of memory?

Using New Approaches in Neurobiology to Rethink Stress-Induced Amnesia

Purpose of Review

Psychological stress can impact memory systems in several different ways. In individuals with healthy defense and coping systems, stress results in the formation of negatively valenced memories whose ability to induce emotional and somatic distress subsides with time. Vulnerable individuals, however, go on to develop stress-related disorders such as post-traumatic stress disorder (PTSD) and suffer from significant memory abnormalities. Whether expressed as intrusive trauma memories, partial amnesia, or dissociative amnesia, such abnormalities are thought to be the core source of patients' symptoms, which are often debilitating and implicate an entire socio-cognitive-affective spectrum.

Recent Findings

With this in mind, and focusing on stress-responsive hippocampal microcircuits, this article highlights recent advances in the neurobiology of memory that allow us to (1) isolate and visualize memory circuits, (2) change their activity using genetic tools and state-dependent manipulations, and (3) directly examine their impact on socio-affective circuits and global network connectivity. By integrating these approaches, we are now in a position to address important questions that have troubled psychiatry for a long time-questions such as are traumatic memories special, and why are stress effects on memory diverse.

Summary

Furthering our fundamental understanding of memory in the framework of adaptive and maladaptive stress responses has the potential to boost the development of new treatments that can benefit patients suffering from psychological trauma.

The Research on the Relationship of RAGE, LRP-1, and Aβ Accumulation in the Hippocampus, Prefrontal Lobe, and Amygdala of STZ-Induced Diabetic Rats

Diabetes mellitus (DM) has been regarded as an important risk factor for Alzheimer's disease (AD), and diabetic patients and animals have shown cognitive dysfunction. More research has shown that the amyloid-β (Aβ), which is a hallmark of AD, was found deposited in the hippocampus of diabetic rats. This Aβ accumulation is regulated by the receptor for advanced glycation end products (RAGE) and low-density lipoprotein receptor-related protein (LRP-1). However, the expression of RAGE and LRP-1 in diabetic rats is not very clear. In the present study, we used streptozotocin (STZ)-induced diabetic rats to investigate whether the expression of RAGE and LRP-1 is related to Aβ_1-42 deposition at the hippocampus, prefrontal lobe, and amygdala in DM. We found that diabetic rats had longer escape latency and less frequency of entrance into the target zone than that of the control group (P < 0.05) in the Morris water maze (MWM) test. The Aβ_1-42 expression in the hippocampus and prefrontal lobe significantly increased in the DM group compared to the control group (P < 0.05). RAGE increased (P < 0.05), while LRP-1 decreased (P < 0.05) in the hippocampus tissue and prefrontal lobe tissue of DM rats. The Aβ_1-42 deposition was correlated with RAGE positively (P < 0.05), but with LRP-1 negatively (P < 0.05). Further, the expression levels of Aβ_1-42, RAGE, and LRP-1 were not changed in the amygdala between the diabetic rats and the control group. These findings indicated that upregulating RAGE and/or downregulating LRP-1 at the hippocampus and the prefrontal lobe contributed to the Aβ_1-42 accumulation and then further promoted the cognitive impairment of diabetic rats.