Diagnosis of psychiatric disorders in humans is based on comparing individuals to the normal population. However, many animal models analyze averaged group effects, thus compromising their translational power. This discrepancy is particularly relevant in posttraumatic stress disorder (PTSD), where only a minority develop the disorder following a traumatic experience. In our PTSD rat model, we utilize a novel behavioral profiling approach that allows the classification of affected and unaffected individuals in a trauma-exposed population. Rats were exposed to underwater trauma (UWT) and four weeks later their individual performances in the open field and elevated plus maze were compared to those of the control group, allowing the identification of affected and resilient UWT-exposed rats. Behavioral profiling revealed that only a subset of the UWT-exposed rats developed long-lasting behavioral symptoms. The proportion of affected rats was further enhanced by pre-exposure to juvenile stress, a well-described risk factor of PTSD. For a biochemical proof of concept we analyzed the expression levels of the GABAA receptor subunits α1 and α2 in the ventral, dorsal hippocampus and basolateral amygdala. Increased expression, mainly of α1, was observed in ventral but not dorsal hippocampus of exposed animals, which would traditionally be interpreted as being associated with the exposure-resultant psychopathology. However, behavioral profiling revealed that this increased expression was confined to exposed-unaffected individuals, suggesting a resilience-associated expression regulation. The results provide evidence for the importance of employing behavioral profiling in animal models of PTSD, in order to better understand the neural basis of stress vulnerability and resilience.

Pre-pubertal stress increases post-traumatic stress disorder (PTSD) susceptibility. We have previously demonstrated that enriched environment (EE) intervention immediately after pre-pubertal stress protects from the effects of trauma in adulthood. Here, we examined whether exposure to EE would also be beneficial if applied after exposure to trauma in adulthood. We have recently shown that exposure to juvenile stress and under-water trauma (UWT) is associated with increased expression of GABAA receptor subunit α1 in the ventral hippocampus. However, differentiating between affected and unaffected individuals, this increased expression was confined to stress-exposed, behaviorally unaffected individuals, suggesting upregulation of α1 expression as a potential mechanism of resilience. We now examined whether EE-induced resilience renders increased expression of α1 in the ventral hippocampus redundant when facing a trauma later in life. Adult rats were exposed to UWT, with pre-exposure to juvenile stress, and tested in the open field and elevated plus maze paradigms four weeks later. EE exposure during juvenility prevented pre-pubertal stress-induced vulnerability, but not if performed following UWT in adulthood. Furthermore, juvenile EE exposure prevented the trauma-associated increase in α1 expression levels. Our findings emphasize the importance of early interventions in order to reduce the likelihood of developing psychopathologies in adulthood.

The ability to manipulate and selectively position cells into patterns or distinct microenvironments is an important component of many single cell experimental methods and biological engineering applications. Although a variety of particles and cell patterning methods have been demonstrated, most of them deal with the patterning of cell populations, and are either not suitable or difficult to implement for the patterning of single cells. Here, we describe a bottom-up strategy for the micropatterning of cells and cell-sized particles. We have configured a micromanipulator system, in which a pneumatic microinjector is coupled to a holding pipette capable of physically isolating single particles and cells from different types, and positioning them with high accuracy in a predefined position, with a resolution smaller than 10 µm. Complementary DNA sequences were used to stabilize and hold the patterns together. The system is accurate, flexible, and easy-to-use, and can be automated for larger-scale tasks. Importantly, it maintains the viability of live cells. We provide quantitative measurements of the process and offer a file format for such assemblies.

The search for therapeutic strategies to promote neuronal regeneration following injuries toward functional recovery is of great importance. Brief low-frequency electrical stimulation (ES) has been reported as a useful method to improve neuronal regeneration in different animal models; however, the effect of ES on single neuron behavior has not been shown. Here, we study the effect of brief ES on neuronal regeneration of the CNS of adult medicinal leeches. Studying the regeneration of selected sets of identified neurons allow us to quantify Significance Statement Recent studies have demonstrated that brief electrical stimulation (ES) can improve neuronal regeneration. However, the effect of ES on single neuron behavior has not been shown. In the current study, we use a relatively simple nervous system, the adult medicinal leech, label identify neurons, and study the effects of ES on their regeneration. We show that different neurons response differently to the same ES paradigm. Following brief ES (20 Hz, 30 min), more neuronal branches of the Retzius cells traverse the injury site with better directed growth. In addition, more microglial cells were detected in proximity to the stimulation site compared with the non-stimulated nervous systems. We conclude that ES triggers efficient neuronal regeneration and this effect might be mediated through differential microglial distribution.

Resilience has been conceptualized in part as a dynamic process that includes the ability to adapt to stressful conditions. As such it encompasses the extent to which neural plasticity may be promoted. The current study examined metaplasticity by referring to the “plasticity of synaptic plasticity” in a neural circuit composed of the basolateral amygdala (BLA) and the nucleus accumbens (NAcc), using behavioural stress controllability with or without preceding stimulation of the dorsal periaqueductal gray (i.e. dPAG priming). A tendency for increased plasticity in the controllable versus the uncontrollable group was found in both the BLA and NAcc. dPAG priming suppressed NAcc LTP in all groups, but it suppressed BLA LTP only in the uncontrollable group, demonstrating dissociation between either controllable and uncontrollable groups or the NAcc and BLA. Thus, metaplasticity in the dPAG-BLA-NAcc circuit regulated differentially by controllable or uncontrollable stress may underlie stress coping, and thus contribute to stress-related psychopathologies.