Alcohol use disorder (AUD) is the leading cause of substance use disorders among Veterans and 55 to 75% of the population that are diagnosed with PTSD also receive a comorbid diagnosis of AUD. The co-diagnosis of PTSD/AUD is associated with neurocognitive changes such as increased impulsivity and risk-taking behavior, especially among individuals with combat-related trauma. Furthermore, increased neuroinflammation in subregions of the prefrontal cortex (PFC) are suggested to contribute to these neurocognitive changes. To better understand the cognitive deficits associated with co-occurring PTSD/AUD we incorporated a probabilistic discounting task (PDT) to model risk-based decision-making in male and female Wistar rats that were exposed to restraint stress (RS) and chronic intermittent ethanol exposure (CIE). Following RS and CIE, rats underwent lever press training through a series of different training phases, in which one lever delivered a small reward 100% of the time, and the other a large reward, delivered with descending probability each trial block. Pressing the large-reward lever during the final two trial blocks when it is disadvantageous to do so is considered “risky” behavior. A week prior to PDT, rats were treated prophylactically with CDPPB, a positive allosteric modulator of the metabotropic glutamate type 5 (mGlu5) receptor, to determine if the cognitive deficits caused by stress and alcohol exposure could be prevented. Additionally, to determine if our model mimicked the neuroinflammatory mechanism seen in the human condition and the therapeutic effects of CDPPB, we assessed TNF-⍺ protein expression in a subset of rats. Our results indicated that male rats exposed to RS and CIE had significantly greater responding during the 3rd, 4th, and 5th risk blocks compared to all other groups. However, the administration of CDPPB reversed this effect. Females exposed to RS and CIE only displayed increased risky behavior at the highest risk block and this was also blocked with the administration of CDPPB. We also determined that RS and CIE significantly increased TNF-⍺ levels in the IfL cortex compared to either RS or CIE alone and the prophylactic administration of CDPPB reduced TNF-⍺ protein expression to control animal levels. In the present study, we demonstrate that exposure to stress and chronic alcohol leads to significant neurocognitive deficits resulting in increased risky decision-making, but these deficits can be attenuated through modulation of the mGlu5 receptor prior to behavioral testing. Additionally, these deficits could be due to deleterious neuroinflammation in subregions of the PFC.

Depression occurs in about one third of patients with stroke and cardiac arrest. Hyperactivity of the stress system is the most commonly observed neuroendocrine change in major depressive disorder (MDD), which involves elevated levels in the cerebrospinal fluid of corticotropin-releasing hormone (CRH), a key stress neurohormone. Substantial evidence suggests that normalization of the stress system may be a requirement for successful treatment of MDD through region-specific changes in the mesocorticolimbic circuitry. Thus, alteration in the stress system may underlie the emotional and functional impairments observed following brain ischemic events. In addition, recent findings suggest that ischemic brain injury triggers a restorative process, creating a cerebral environment similar to that of early brain development, a period characterized by rapid neuronal growth and neuroplasticity, critical to optimize functional recovery of individuals post stroke. In particular brain-derived neurotrophic factor (BDNF), has been shown to play an important role in the pathophysiology of major depression and cerebral ischemia. However, whether CRH can mediate the expression of BDNF in the reparative process triggered by ischemic injury remains to be characterized. Therefore, the purpose of the current thesis is to characterize the effect of pharmacological blockade of CRH signaling at the onset of a global ischemic stroke, on emotional and cognitive behaviors, alteration in the neuroendocrine stress system, and markers of neuroplasticity including BDNF. To do this, an animal model of global cerebral ischemia with subsequent behavioral testing and postmortem brain analysis was used to determine underlying biochemical and behavioral changes modulated by CRH signaling following brain ischemia. This doctoral work will help elucidate the relationship between CRH and BDNF in the context of cerebral ischemia, and may provide insights for therapies targeting the stress system. These studies address considerations such as: the interplay between stress, neuroplasticity and emotionality, and whether global ischemia can affect mood via changes in the HPA axis response.

Due to the persisting lack of reliable animal models of cognitive impairment with good translational validity, researches strive to discover new ways and tools to replicate symptoms of human neurodegenerative diseases in rodents. Recently, biperiden, an M1- selective muscarinic antagonist, has been proposed as a potential tool for generating fast screening models of mnemonic deficits such as seen in patients with Alzheimer's disease. Being highly selective for the M1 receptor, a predominant type of muscarinic acetylcholine receptors in the brain involved in cognitive processes, it has been speculated to possibly only influence cognition without causing sensorimotor side effects. Studies assessing the usability of this drug reported conflicting results. We have decided to expand the experimental data and evaluate biperiden's validity in several variants of the Morris water maze. The results of this study showed no significant effect of biperiden on cognitive flexibility, tested by reversal learning. In delayed-matching-to-position paradigm, which tests assesses working memory, we found a difference in performance between the two experimental groups; however, it cannot be unequivocally attributed to a memory impairment. No effects were observed in visible platform task, confirming a lack of...