Traumatic brain injury (TBI) is a severe condition and a major cause of death and disability. There is no pharmacological treatment available in clinical practice today and knowledge of brain injury mechanisms is of importance for development of neuroprotective drugs. The aims of the thesis were to get a better understanding of astrocyte reactions and immune responses, as well as behavioral changes after focal unilateral cortical contusion injury and diffuse bilateral central fluid percussion injury in rats and mice. In the focal injury models, the astrocyte reactions were generally restricted to the ipsilateral hemisphere. After diffuse TBI, vimentin and glial fibrillary acidic protein (GFAP) positive reactive astrocytes were bilaterally expressed in brain regions even distant from the injury site, including regions where axonal injury was seen. Early after diffuse TBI, there was a robust immune response, including activation of macrophages/microglia (Mac-2+) and infiltration of neutrophils (GR-1+) and T-cells (CD3+). In order to measure functional outcome, the recently established Multivariate Concentric Square Field™ (MCSF) test for complex behaviors, including risk taking and explorative strategies was used. The Morris water maze (MWM) was applied for testing learning and memory. The MCSF test revealed alterations in risk taking, risk assessment and exploratory behavior, in the mice subjected to focal injury whereas mice subjected to the diffuse injury showed a deviant stereotyped behavior. After focal injury mice showed a decreased ability to adapt to the arena in the second trial, when tested repeatedly in the MCSF test. Mice subjected to diffuse injury had an impaired memory but not learning, in the MWM test. Post-injury treatment with the anti-inflammatory anti-interleukin-1β (IgG2 a/k) antibody showed a positive effect on functional outcome in the diffuse injury model. Altogether, the results demonstrate that focal and diffuse TBI models produce differences in cellular reactions and behavioral outcome and that the immune response plays a key role in the pathology after brain injury.

Excessive and compulsive ethanol drinking is one of the most serious public health issues. Therefore, it is vital to increase the knowledge about risks and protection for alcohol use disorders (AUD) to optimize prevention and treatment strategies. Ethanol consumption commonly initiates during adolescence when extensive neuronal maturation and development also occurs. Early exposure to ethanol is a risk factor for AUD, but the effects of adolescent drinking and the basis for the individual susceptibility to AUD are not fully understood. The interactions between genotype and environmental factors determine the individual risk for AUD and this thesis aimed to examine the environmental impact. The specific aims were to investigate 1) how early-life conditions affect adolescent voluntary ethanol drinking, behavioural profiles, endogenous opioids and response to treatment with an opioid antagonist (naltrexone), and 2) whether alterations detected in the offspring may be mediated by variations in maternal behaviour. A rodent maternal separation (MS) model was used to mimic a protective and risk-inducing early-life environment, respectively, with the use of 15 min (MS15) or 360 min (MS360) of daily MS. The main findings were 1) the MS360, but not the MS15 rats, responded to naltrexone following adolescent ethanol drinking; all adolescent rats had a high voluntary ethanol intake independent of early environmental conditions whereas in the adult groups the MS360, but not the MS15 rats, increased their ethanol intake and preference over time; adolescent ethanol exposure resulted in higher dynorphin levels in hippocampus and higher Met-enkephalin-Arg6Phe7 in the amygdala, independently of rearing conditions, 2) behavioural profiling using the multivariate concentric square field™ test showed: the young MS360 rats had increased risk assessment and risk taking behaviour compared to the young MS15 rats; the young MS15 rats increased, whereas the young MS360 rats decreased, their risk assessment and risk taking behaviour over time; differences in pup-retrieval strategies where the MS360 dams retrieved some pups into a safe area but as compared to MS15 rats they left more pups in a risk area; increased risk assessment behaviour in the MS360 dams immediately after weaning. Taken together, early-life environmental conditions alter adult but not adolescent drinking, the response to naltrexone, and behaviour in dams and offspring. Adolescent rats consumed more ethanol independent of rearing conditions and displayed increased opioid levels in brain areas related to cognition and addiction.

Alcohol use disorder is a worldwide public health problem and is a disorder with substantial individual variation. There are suggested links between various behavioral traits, comorbid psychiatric diseases and excessive alcohol consumption. Moreover, the endogenous opioid system is involved in alcohol reward and reinforcement, and implicated in the action of alcohol. However, less is known about the complex associations between individual differences in behavior, alcohol consumption, pharmacotherapy response and related neurochemical mechanisms. Experimental animal models are critical for understanding the neurobiological underpinnings of alcohol use disorder. The overall aims of this thesis were: i) to study the association between behavior and voluntary alcohol intake in outbred rats; ii) to study the association of voluntary alcohol intake, behavior, opioid receptor density and response to naltrexone; and iii) to obtain detailed behavioral characterizations of the animals on the basis of their voluntary alcohol intake. The results revealed that the multivariate concentric square fieldTM (MCSF) test was a complementary method for understanding mechanisms underlying various mental states. The MCSF broadened the perspective on risk-related behaviors, including aspects of risk assessment. Individual differences in alcohol intake using the modified intermittent access paradigm enabled analyses of drinking patterns in high and low alcohol-drinking rats. There was an alcohol deprivation effect in high-drinking animals only. The behavior profiling of high alcohol drinking- rats before and after alcohol access suggested that this subgroup was consuming alcohol for its anxiolytic properties. Long-lasting changes were found in the mu and the delta opioid receptors after long-term, intermittent voluntary alcohol intake; some of these changes are in line with findings in humans. The voluntary alcohol consumption and the concomitant response to naltrexone were different for Wistar rats from different suppliers. Moreover, the Rcc Wistar rats may be more suitable for studies of alcohol use disorders due to increasing alcohol intake and the presence of a high-drinking subpopulation with increasing alcohol intake over time. The high-drinking subpopulation showed pronounced effects of naltrexone on alcohol intake. In conclusion, studies of individual differences increase understanding of variability in behavior, pharmacotherapy response and factors involved in vulnerability of alcohol use disorders.

Genes and environment interact to determine an individual’s vulnerability or resilience to several psychiatric disorders, including alcohol use disorder (AUD). Alcohol use is often initiated during adolescence and early onset drinking is associated with increased risk for later AUD. Childhood and adolescence are periods of extensive brain maturation, which makes young individuals more susceptible to environmental influence. However, little is known about early environmental influence on reward pathways and behaviors involved in the development of AUD. Changes in the endogenous opioid and dopamine systems, as well as individual differences in risk behaviors are all believed to play important roles in the increased vulnerability seen after adverse early life events and early onset drinking. The overall aim of the thesis was therefore to investigate the influence of early environmental factors on adolescent alcohol intake, endogenous opioids, dopamine dynamics and alcohol-induced effects in rats to increase our knowledge of neurobiological factors underlying vulnerability to AUD. Furthermore, individual behavioral differences and their correlation to basal and drug-induced neurobiological responses in rats were also investigated. Animal models of different early environments, e.g. maternal separation and social vs. single housing, and adolescent alcohol consumption have been used to study effects on behavior, endogenous opioid peptides and dopamine dynamics. The results identified the amygdala and dorsal striatum as interesting brain regions in which endogenous opioids and dopamine, respectively, are impacted by early environmental factors. The amygdala and the dorsal striatum are both hypothesized to be involved in the shift from initial drug use to compulsive use and changes in these areas may be underlying environmentally increased vulnerability to AUD. Furthermore, behavioral phenotypes in relation to individual neurobiological responses were identified. High risk-taking behavior was associated with a more pronounced response to amphetamine, but the inherent dopamine response was instead associated with risk-assessment behavior. In conclusion, several brain regions of interest for future research were identified. Furthermore, the results contribute to increased understanding of factors involved in the development of vulnerability for AUD in adolescents and young adults.

Indiana University-Purdue University Indianapolis (IUPUI) / Alcoholism inheritance rates have been estimated as high as 60% in a human population. Many significant features of alcohol dependence have been replicated in rodent animal models of alcoholism, however not in totality. These animal models include inbred preferring (iP) and nonpreferring (iNP) rat types. Congenic rats have been engineered from the iP and iNP strains whereby a P congenic rat has in its genome a well-chosen chromosomal portion taken from an NP rat (P.NP) and, reciprocally, an NP congenic rat has acquired the analogous DNA from a P rat (NP.P). In this case, a quantitative trait locus (QTL) from chromosome 4 is the donor genetic material for the congenic rats. It is of great interest to further study this chromosome 4 QTL because it has been found to control a significant portion of ethanol consumption behavior in iP and iNP rats. This study aimed to behaviorally profile the iP, iNP and reciprocal congenic rats. As a result of the behavioral profiling of these genetically related groups, some conclusions could be made regarding which behaviors appear to be controlled by the chromosome 4 donor DNA.This study primarily utilized the Multivariate Concentric Square Field apparatus (MCSF) to characterize behavioral profiles for the inbred and congenic rats. The Open field (OF) and Elevated plus maze (EPM) supported this effort. The MCSF is valuable in that it allows for the animals to interact within an environment that has ethological value. The 12 different zones that make up the field are characterized by some functional quality in terms of type and duration of behavior performed, etc. The behavioral data is aggregated and finally represented in terms of five functional categories, the elements of the behavioral profile: general activity, exploratory activity, risk assessment, risk taking, and shelter seeking. The study hypotheses were shaped by prior research suggesting that iPs should display lower general activity and risk taking strategy than iNPs in the MCSF. Inbred Ps should be more active in the OF and spend more time in the center of the EPM. Generally, it is expected that the iP QTL confer behavioral phenotypes to the iNP strain that deviate toward a "P" behavioral phenotype and reciprocally, the iNP QTL confer behavioral phenotypes to the iP strain that deviate toward an "NP" behavioral phenotype. The results showed that iP rats performed more risk assessment and risk taking behavior and less shelter seeking and anxiety-like behavior than iNP rats. It followed that P.NP congenic rats significantly downgraded their risk assessment and risk taking behavior when compared to iP rats. This decrease can be attributed to the chromosome 4 QTL donated from the iNP breed. All together this study concludes that risk assessment and risk taking behavior in the iP rats is controlled by the same DNA region that, in part, determines voluntary intake of ethanol consumption. Further fine mapping of the QTL region should help in discovering if the same DNA sequences that influence ethanol intake also significantly influence risk behavior.