Behavioral training and predisposed coping strategies interact to influence resilience in male Long-Evans rats: Implications for depression

Abstract

Effective coping strategies and adaptive behavioral training build resilience against stress-induced pathology. Both predisposed and acquired coping strategies were investigated in rats to determine their impact on stress responsiveness and emotional resilience. Male Long-Evans rats were assigned to one of the three coping groups: passive, active, or variable copers. Rats were then randomly assigned to either an effort-based reward (EBR) contingent training group or a non-contingent training group. Following EBR training, rats were tested in appetitive and stressful challenge tasks. Physiological responses included changes in fecal corticosterone and dehydroepiandrosterone (DHEA) metabolites as well as neuropeptide Y (NPY)-immunoreactivity in the hippocampus and amygdala. Regardless of a rat's predisposed coping strategy, EBR rats persisted longer than non-contingent rats in the appetitive problem-solving task. Furthermore, training and coping styles interacted to yield the seemingly most adaptive DHEA/corticosterone ratios in the EBR-trained variable copers. Regardless of training group, variable copers exhibited increased NPY-immunoreactivity in the CA1 region.

Disruption of peri-adolescent endocannabinoid signaling modulates adult neuroendocrine and behavioral responses to stress in male rats

“…During the second session, the duration of time spent engaging in passive (immobility) or active (swimming and struggling) coping behaviors (Bardi et al, 2012;Lu et al, 2008) was videotaped and scored by an experimenter blind to treatment conditions. Immobility was defined as the rat remaining stationary with minimal movement of limbs to remain afloat.…”

Profiling coping strategies in male and female rats: Potential neurobehavioral markers of increased resilience to depressive symptoms

“…Using this technique to profile coping strategies in rats, flexible copers have been found to exhibit significantly more Neuropeptide Y (NPY)-immunoreactive cells, associated with emotional resilience, in the basolateral amygdala and bed nucleus of the stria terminalis than the other coping groups following exposure to chronic unpredictable stress (Hawley et al, 2010). In another study, following a cognitive training program with no chronic stress exposure, flexible rats exhibited higher levels of NPY- immunoreactive cells in the CA1 and CA3 hippocampal subfields than their passive and active counterparts (Bardi et al, 2012). When exposed to the activity-stress paradigm, in which animals are housed in running wheels and fed one hour per day prompting excessive spontaneous levels of running, the flexible copers exhibited lower fecal corticoisteroid metabolites than the other coping groups (Lambert et al, 2006).…”

“…Rats profiled with a flexible coping phenotype, for example, exhibit increased neurobiological markers of emotional regulation compared to active and passive copers (Bardi et al, 2012; Lambert et al, 2014). In the current study, responses of male and female rats to prediction errors in a spatial foraging task (dry land maze; DLM) were examined after animals were exposed to chronic unpredictable stress (CUS).…”

Contingency-based emotional resilience: effort-based reward training and flexible coping lead to adaptive responses to uncertainty in male rats

“…In recent studies in our laboratory, an alternative to the learned helplessness model, that is, learned persistence, has been investigated as a model of enhanced emotional resilience in the midst of uncertainty related to response outcomes (Lambert, 2006; Bardi et al, 2012, 2013). Specifically, effort-based reward (EBR) training, in which rodents are trained to dig for food rewards in a large arena daily for several weeks, is utilized to build response-outcome contingencies.…”

“…When presented with a novel, unsolvable problem-solving task, contingency-trained rats were observed to persist longer on the task than comparable noncontingency-trained animals. Further, the contingency-trained animals had higher dehydroepiandrosterone (DHEA)/corticosteroid (CORT) ratios (Bardi et al, 2012); higher levels of DHEA have been associated with adaptive behavioral responses to stress as well as neurotrophic effects (Karishma and Herbert, 2002). Considering that diminished levels of DHEA have been observed in psychiatric illness such as anxiety, depression and schizophrenia (Morgan et al, 2009), altered DHEA/CORT ratios following EBR training may have contributed to learned persistence in the aforementioned problem solving task.…”