Traumatic brain injuries during development disrupt dopaminergic signaling

Amphetamine and methylphenidate potential on the recovery from stroke and traumatic brain injury: a review

The prevalence of stroke and traumatic brain injury is increasing worldwide. However, current treatments do not fully cure or stop their progression, acting mostly on symptoms. Amphetamine and methylphenidate are stimulants already approved for attention deficit hyperactivity disorder and narcolepsy treatment, with neuroprotective potential and benefits when used in appropriate doses. This review aimed to summarize pre-clinical and clinical trials testing either amphetamine or methylphenidate for the treatment of stroke and traumatic brain injury. We used PubMed as a database and included the following keywords ((methylphenidate) OR (Ritalin) OR (Concerta) OR (Biphentin) OR (amphetamine) OR (Adderall)) AND ((stroke) OR (brain injury) OR (neuroplasticity)). Overall, studies provided inconsistent results regarding cognitive and motor function. Neurite outgrowth, synaptic proteins, dendritic complexity, and synaptic plasticity increases were reported in pre-clinical studies along with function improvement. Clinical trials have demonstrated that, depending on the brain region, there is an increase in motor activity, attention, and memory due to the stimulation of the functionally depressed catecholamine system and the activation of neuronal remodeling proteins. Nevertheless, more clinical trials and pre-clinical studies are needed to understand the drugs' full potential for their use in these brain diseases namely, to ascertain the treatment time window, ideal dosage, long-term effects, and mechanisms, while avoiding their addictive potential.

Dysregulation of the dopaminergic system secondary to traumatic brain injury: implications for mood and anxiety disorders

Traumatic brain injury (TBI) represents a public health issue with a high mortality rate and severe neurological and psychiatric consequences. Mood and anxiety disorders are some of the most frequently reported. Primary and secondary damage can cause a loss of neurons and glial cells, leading to dysfunction of neuronal circuits, which can induce imbalances in many neurotransmitter systems. Monoaminergic systems, especially the dopaminergic system, are some of the most involved in the pathogenesis of neuropsychiatric and cognitive symptoms after TBI. In this work, we summarize the studies carried out in patients who have suffered TBI and describe alterations in the dopaminergic system, highlighting (1) dysfunction of the dopaminergic neuronal circuits caused by TBI, where modifications are shown in the dopamine transporter (DAT) and alterations in the expression of dopamine receptor 2 (D2R) in brain areas with dopaminergic innervation, thus establishing a hypodopaminergic state and (2) variations in the concentration of dopamine and its metabolites in biological fluids of post-TBI patients, such as elevated dopamine (DA) and alterations in homovanillic acid (HVA). On the other hand, we show a large number of reports of alterations in the dopaminergic system after a TBI in animal models, in which modifications in the levels of DA, DAT, and HVA have been reported, as well as alterations in the expression of tyrosine hydroxylase (TH). We also describe the biological pathways, neuronal circuits, and molecular mechanisms potentially involved in mood and anxiety disorders that occur after TBI and are associated with alterations of the dopaminergic system in clinical studies and animal models. We describe the changes that occur in the clinical picture of post-TBI patients, such as alterations in mood and anxiety associated with DAT activity in the striatum, the relationship between post-TBI major depressive disorders (MDD) with lower availability of the DA receptors D2R and D3R in the caudate and thalamus, as well as a decrease in the volume of the substantia nigra (SN) associated with anxiety symptoms. With these findings, we discuss the possible relationship between the disorders caused by alterations in the dopaminergic system in patients with TBI.

Association between pediatric TBI and mental health and substance use disorders: A scoping review

BACKGROUND

The relationship between pediatric Traumatic Brain Injury (TBI) and long-term mental health and substance use disorders is not well known, resulting in inadequate prevention and management strategies. The aim of this scoping review is to review the evidence on pediatric TBI and the development of mental health disorders and substance use later in life and to identify gaps in the literature to inform future research.

METHODS

We searched multiple databases for original articles published between September 2002 and September 2022 on TBI-related mental health and/or substance use disorders in children and youth. Two independent reviewers performed the screening using Arksey and O'Malley and Levac et al.'s scoping review framework.

RESULTS

A total of six papers are included in this scoping review. Studies included are comprised of cross-sectional and prospective longitudinal cohort studies.

DISCUSSION

A correlation between pediatric TBI and development of certain mental health disorders and substance use is suggested, although much of the current evidence is mixed and does not account for confounding variables. Future studies should aim to closely examine these links and identify modifiers that can influence these relationships.

Rural-Urban Differences in Behavioral Outcomes among Adults with Lifetime History of Traumatic Brain Injury with Loss of Consciousness: 2016-2019 Ohio BRFSS

This study examined if the associations between lifetime history of traumatic brain injury (TBI) with loss of consciousness (LOC) and unhealthy alcohol use or mental health problems differ by location of living (rural vs. urban). The lifetime history data of TBI with LOC, location of living, unhealthy alcohol use (binge drinking, heavy drinking), and mental health problems (depression diagnosis, number of poor mental health days) were sourced from the 2016, 2017, 2018, and 2019 Ohio Behavioral Risk Factory Surveillance Surveys, and the final sample included 16,941 respondents. We conducted multivariable logistic regressions to determine the odds ratios for each of the five outcomes between individuals living in rural vs. urban areas and between individuals with vs. without a lifetime history of TBI with LOC. No interaction between location of living and lifetime history of TBI with LOC was observed for any outcomes, indicating rurality did not modify these relationships. Living in a rural area was associated with decreased binge drinking or heavy drinking but not mental health outcomes. Lifetime history of TBI with LOC was associated with an increased risk of binge drinking, heavy drinking, depression diagnoses, and poor general mental health, regardless of location of living. Our findings support the need for TBI screenings as part of mental health intake evaluations and behavioral health screenings. Though rurality was not associated with mental health outcomes, rural areas may have limited access to quality mental health care. Therefore, future research should address access to mental health services following TBI among rural residents.

Sex and estrous-phase dependent alterations in depression-like behavior following mild traumatic brain injury in adolescent rats

Following mild traumatic brain injury (TBI), high school and collegiate-aged females tend to report more emotional symptoms than males. Adolescent male and female rats (35 days old) were subjected to mild TBI and evaluated for anxiety- and depression-like behaviors using the elevated plus maze and forced swim test (FST), respectively, and cellular alterations. Injured brains did not exhibit an overt lesion, atrophy of tissue or astrocytic reactivity underneath the impact site at 6-week post-injury, suggestive of the mild nature of trauma. Neither male nor female brain-injured rats exhibited anxiety-like behavior at 2 or 6 weeks, regardless of estrous phase at the time of behavior testing. Brain-injured male rats did not exhibit any alterations in immobility, swimming and climbing times in the FST compared to sham-injured rats at either 2- or 6-week post-injury. Brain-injured female rats did, however, exhibit an increase in immobility (in the absence of changes in swimming and climbing times) in the FST at 6 weeks post-injury only during the estrus phase of the estrous cycle, suggestive of a depression-like phenotype. Combined administration of the estrogen receptor antagonist, tamoxifen, and the progesterone receptor antagonist, mifepristone, during proestrus was able to prevent the depression-like phenotype observed during estrus. Taken together, these data suggest that female rats may be more vulnerable to exhibiting behavioral deficits following mild TBI and that estrous phase may play a role in depression-like behavior.

Prescription Opioid Misuse and Sports-Related Concussion Among High School Students in the United States

STUDY OBJECTIVE

Concussion is highly prevalent in adolescents and associated with a higher risk of substance use. With the rising use of opioids among adolescents, one form of substance use of concern is the misuse of prescription opioids. This study aimed to examine the association between a history of sports-related concussion in the past year and current prescription opioid misuse among high school students in the United States.

SETTING

Secondary data analysis from the 2019 Youth Risk Behavior Survey.

PARTICIPANTS

Nationally representative sample of high school students (n = 7314).

DESIGN

Cross-sectional study.

MAIN MEASURES

Participants were asked whether they experienced any concussions related to sports or being physically active during the past 12 months and whether they had any prescription opioid misuse within the past 30 days.

RESULTS

Among this cohort, 14.0% reported sustaining a concussion in the past 12 months and 6% reported current prescription opioid misuse. The prevalence of prescription opioid misuse was higher among those with a history of concussion (9.9%) than among those without concussion (5.5%, P = .002). Controlling for covariates (sex, race/ethnicity, other substance use, depressive symptoms), the odds of prescription opioid misuse was 1.5 times higher for adolescents with concussion than those without (adjusted odds ratios [aOR] = 1.5; 95% CI, 1.0-2.3; P = .029).

CONCLUSION

Concussion was associated with prescription opioid misuse among the US youth, even after accounting for depressive symptoms and other substance use. Longitudinal studies are needed to test causal relationships and understand biobehavioral mechanisms that underlie associations between concussion and opioid misuse in adolescents.

Traumatic Brain Injury and Treatment of Behavioral Health Conditions

Traumatic brain injury (TBI) is a common neurological condition that results from an external force altering normal brain function, whether temporarily or permanently. A concussion is one type of TBI. TBIs vary greatly in severity, which concomitantly creates tremendous variability in their manifestation. The fingerprint of TBI is damage to the frontal areas of the brain, which, with sufficient magnitude, results in impairment of a person's ability to regulate cognition, emotion, and behavior. These consequences of TBI make recognition in the context of treating behavioral health conditions of utmost importance. TBI not only causes behavioral health problems but also produces associated deficits that can undermine the effectiveness of treatment for a behavioral health condition. This overview delineates key characteristics of TBI and describes its association with behavioral health conditions. Mechanisms underlying the relationship between TBI and behavioral health are presented, and a series of recommendations for professionals are proposed. This article is intended to raise awareness about TBI and simultaneously introduce key concepts for accommodating the effects of TBI in behavioral health care.

Role of the Dopaminergic System in the Striatum and Its Association With Functional Recovery or Rehabilitation After Brain Injury

Disabilities are estimated to occur in approximately 2% of survivors of traumatic brain injury (TBI) worldwide, and disability may persist even decades after brain injury. Facilitation or modulation of functional recovery is an important goal of rehabilitation in all patients who survive severe TBI. However, this recovery tends to vary among patients because it is affected by the biological and physical characteristics of the patients; the types, doses, and application regimens of the drugs used; and clinical indications. In clinical practice, diverse dopaminergic drugs with various dosing and application procedures are used for TBI. Previous studies have shown that dopamine (DA) neurotransmission is disrupted following moderate to severe TBI and have reported beneficial effects of drugs that affect the dopaminergic system. However, the mechanisms of action of dopaminergic drugs have not been completely clarified, partly because dopaminergic receptor activation can lead to restoration of the pathway of the corticobasal ganglia after injury in brain structures with high densities of these receptors. This review aims to provide an overview of the functionality of the dopaminergic system in the striatum and its roles in functional recovery or rehabilitation after TBI.

Mild traumatic brain injury increases vulnerability to cerebral ischemia in mice

Recent studies have reported that TBI is an independent risk factor for subsequent stroke. Here, we tested the hypothesis that TBI would exacerbate experimental stroke outcomes via alternations in neuroimmune and neurometabolic function. We performed a mild closed-head TBI and then one week later induced an experimental stroke in adult male mice. Mice that had previously experienced TBI exhibited larger infarcts, greater functional deficits, and more pronounced neuroinflammatory responses to stroke. We hypothesized that impairments in central metabolic physiology mediated poorer outcomes after TBI. To test this, we treated mice with the insulin sensitizing drug pioglitazone (Pio) after TBI. Pio prevented the exacerbation of ischemic outcomes induced by TBI and also blocked the induction of insulin insensitivity by TBI. However, tissue respiratory function was not improved by Pio. Finally, TBI altered microvascular responses including promoting vascular accumulation of serum proteins and significantly impairing blood flow during the reperfusion period after stroke, both of which were reversed by treatment with Pio. Thus, TBI appears to exacerbate ischemic outcomes by impairing metabolic and microvascular physiology. These data have important implications because TBI patients experience strokes at greater rates than individuals without a history of head injury, but these data suggest that those strokes may also cause greater tissue damage and functional impairments in that population.

Paternal exposure to exercise and/or caffeine and alcohol modify offspring behavioral and pathophysiological recovery from repetitive mild traumatic brain injury in adolescence

Only recently has the scope of parental research expanded to include the paternal sphere with epidemiological studies implicating stress, nutrition and alcohol consumption in the neurobiological and behavioral characteristics of offspring. This study was designed to determine if paternal exposure to caffeine, alcohol and exercise prior to conception would improve or exacerbate offspring recovery from adolescent repetitive mild traumatic brain injury (RmTBI). Sires received 7 weeks of standard drinking water, or caffeine and ethanol and were housed in regular cages or cages with running wheels, prior to being mated to control females. At postnatal day 40, offspring were administered RmTBI or sham injuries and were assessed for post concussive symptomology. Post-mortem quantitative real-time polymerase chain reaction (qRT-PCR) was used to assess gene expression in the prefrontal cortex (PFC), nucleus accumbens (NAc) and changes in telomere length. Additionally, enzyme-linked immunosorbent assay (ELISA's) were run on serum to detect levels of cytokines, chemokines and sex hormones. Paternal experience did not improve or exacerbate RmTBI behavioral outcomes. However, female and male offspring displayed unique responses to RmTBI and paternal experience, resulting in changes in physical, behavioral and molecular outcomes. Injury and paternal exercise modified changes in female offspring, whereas male offspring were affected by paternal exercise, caffeine and alcohol treatment. Additionally, paternal experience and RmTBI modified expression of many genes in the PFC, NAc, telomere length and levels of sex hormones. Although further exploration is required to understand the heterogeneity that exists in disease risk and resiliency, this study provides corroborating evidence that paternal experiences prior to conception influences offspring development.

Traumatic brain injury substantially reduces the conditioned reinforcing effects of environmental cues in rats

Traumatic brain injury affects millions of people each year and is an established risk factor for addiction. Recent animal studies have causally demonstrated that injuries can increase drug self-administration across a variety of substances. One potential behavioral mediator for this finding is an increased responsivity to drug-associated cues. This endophenotype can be identified by profiling non-drug-related behaviors. The current study evaluated several paradigms (conditioned approach, conditioned reinforcement, extinction from variable interval responding, conditioned facilitation) to determine how rats with a frontal TBI differed in their response to Pavlovian conditioning in response to food-paired cues. Surprisingly, rats with a TBI demonstrated increased goal-tracking in a conditioned approach paradigm and exerted less effort for a conditioned reinforcer. Moreover, they had slightly facilitated extinction (as demonstrated by significantly larger interresponse times) in the face of reinforcer-associated cues. Despite these effects, TBI rats still demonstrated conditioned facilitation to an auditory stimulus. Together, these effects suggest a phenotype in the opposite direction of what might be anticipated. Cues still served a strong discriminative function and altered behavior; however, they did not function as strong conditioned reinforcers for TBI animals. One potential reason for this is that substantial changes to the dopamine system after TBI may reduce the conditioned reinforcing effects of cues, but sensitize the brain to potent drugs of abuse. More research will be needed to determine whether this is the case.

Alcohol misuse and traumatic brain injury: a review of the potential roles of dopaminergic dysfunction and physiological underarousal post-injury

Although many researchers have demonstrated an increase in alcohol use following traumatic brain injury (TBI), there is also a body of research indicating that alcohol misuse predisposes one to injury and precedes TBI. Accordingly, various mechanisms have been proposed (e.g., self-medication, dampened levels of arousal, dopaminergic dysfunction, etc.) and variable results have emerged. This paper reviews the empirical evidence, for and against, TBI as a risk factor for alcohol misuse. In particular, this paper focuses on the brain-behavior relationships involved and examines the roles of physiological underarousal and dopaminergic dysfunction in the development of alcohol misuse after injury. Alcohol misuse impedes community reintegration among TBI survivors and creates additional rehabilitative challenges. Thus, in order to inform and improve treatment outcomes among this vulnerable population, a deeper understanding of the neural mechanisms implicated is needed.

Brain interrupted: Early life traumatic brain injury and addiction vulnerability

Recent reports provide evidence for increased risk of substance use disorders (SUD) among patients with a history of early-life traumatic brain injury (TBI). Preclinical research utilizing animal models of TBI have identified injury-induced inflammation, blood-brain barrier permeability, and changes to synapses and neuronal networks within regions of the brain associated with the perception of reward. Importantly, these reward pathway networks are underdeveloped during childhood and adolescence, and early-life TBI pathology may interrupt ongoing maturation. As such, maladaptive changes induced by juvenile brain injury may underlie increased susceptibility to SUD. In this review, we describe the available clinical and preclinical evidence that identifies SUD as a persistent psychiatric consequence of pediatric neurotrauma by discussing (1) the incidence of early-life TBI, (2) how preclinical studies model TBI and SUD, (3) TBI-induced neuropathology and neuroinflammation in the corticostriatal regions of the brain, and (4) the link between childhood or adolescent TBI and addiction in adulthood. In summary, preclinical research utilizes an innovative combination of models of early-life TBI and SUD to recapitulate clinical features and to determine how TBI promotes a risk for the development of SUD. However, causal processes that link TBI and SUD remain unclear. Additional research to identify and therapeutically target underlying mechanisms of aberrant reward pathway development will provide a launching point for TBI and SUD treatment strategies.

The potential roles of dopamine in traumatic brain injury: a preclinical and clinical update

Traumatic brain injury (TBI) is one of the leading causes of death and disability, particularly among the young and the elderly. Several therapeutic options have been investigated, including drug interventions or combinational therapies. Although many drugs have shown promising results in the preclinical stage, all have failed in large clinical trials. Targeting the dopamine system is a novel TBI approach that provides benefits to functional outcomes. TBI could damage the dopaminergic system. Alterations in dopamine levels can impact cellular dysfunction and central nervous system (CNS) inflammation. Experimental evidence suggests that dopamine should be considered a first-line treatment to protect cerebral autoregulation and promote cerebral outcomes in TBI. Furthermore, investigation of dopamine-related genetic factors in relation to injury severity could also be of great significance for promoting TBI treatment. Importantly, various clinical lines of evidence have indicated that many dopamine agonists are beneficial when administered following injury in TBI patients. However, side effects of dopamine treatment prevent their use in TBI treatment, and there is a need for ongoing large, prospective, double-blind randomized controlled trials (RCTs) with these medications by the use of standardized criteria and outcomes to fully understand their effectiveness in this patient group. Here, we review the roles of dopamine in TBI and discuss the role that dopaminergic therapies have in neuroprotective strategies.

Cocaine self-administration is increased after frontal traumatic brain injury and associated with neuroinflammation

Traumatic brain injury (TBI) has been linked to the development of numerous psychiatric diseases, including substance use disorder. However, it can be difficult to ascertain from clinical data whether the TBI is cause or consequence of increased addiction vulnerability. Surprisingly few studies have taken advantage of animal models to investigate the causal nature of this relationship. In terms of a plausible neurobiological mechanism through which TBI could magnify the risk of substance dependence, numerous studies indicate that TBI can cause widespread disruption to monoaminergic signaling in striatal regions, and also increases neuroinflammation. In the current study, male Long-Evans rats received either a mild or severe TBI centered over the frontal cortex via controlled cortical impact, and were subsequently trained to self-administer cocaine over 10 6-hour sessions. At the end of the study, markers of striatal dopaminergic function, and levels of inflammatory cytokine levels in the frontal lobes, were assessed via western blot and multiplex ELISA, respectively. There was significantly higher cocaine intake in a subset of animals with either mild or severe TBI. However, many animals within both TBI groups failed to acquire self-administration. Principal components analysis suggested that both dopaminergic and neuroinflammatory proteins were associated with overall cocaine intake, yet only an inflammatory component was associated with acquisition of self-administration, suggesting neuroinflammation may make a more substantial contribution to the likelihood of drug-taking. Should neuroinflammation play a causal role in mediating TBI-induced addiction risk, anti-inflammatory therapy may reduce the likelihood of substance abuse in TBI populations.

Minocycline blocks traumatic brain injury-induced alcohol consumption and nucleus accumbens inflammation in adolescent male mice

Alcohol use is a well characterized risk factor for traumatic brain injury (TBI); however, emerging clinical and experimental research suggests that TBI may also be an independent risk factor for the development of alcohol use disorders. In particular, TBIs incurred early in life predict the development of problem alcohol use and increase vulnerability to neuroinflammation as a consequence of alcohol use. Critically, the neuroinflammatory response to alcohol, mediated in large part by microglia, may also function as a driver of further alcohol use. Here, we tested the hypothesis that TBI increases alcohol consumption through microglia-mediated neuroinflammation. Mice were injured as juveniles and alcohol consumption and preference were assessed in a free-choice voluntary drinking paradigm in adolescence. TBI increased alcohol consumption; however, treatment with minocycline, an inhibitor of microglial activation, reduced alcohol intake in TBI mice to sham levels. Moreover, a single injection of ethanol (2 g/kg) significantly increased microglial activation in the nucleus accumbens and microglial expression of the proinflammatory cytokine IL-1β in TBI, but not sham or minocycline-treated, mice. Our data implicate TBI-induced microglial activation as a possible mechanism for the development of alcohol use disorders.

Repetitive Brain Injury of Juvenile Mice Impairs Environmental Enrichment-Induced Modulation of REM Sleep in Adulthood

Traumatic brain injuries (TBIs) are a common and costly ongoing public health concern. Injuries that occur during childhood development can have particularly profound and long-lasting effects. One common consequence and potential mediator of negative outcomes of TBI is sleep disruption which occurs in a substantial proportion of TBI patients. These individuals report greater incidences of insomnia and sleep fragmentation combined with a greater overall sleep requirement meaning that many patients are chronically sleep-deprived. We sought to develop an animal model of developmental TBI-induced sleep dysfunction. Specifically, we tested the hypothesis that early (postnatal day 21), repeated closed head injuries in Swiss-Webster mice, would impair basal and homeostatic sleep responses in adulthood. Further, we asked whether environmental enrichment (EE), a manipulation that improves functional recovery following TBI and has been shown to alter sleep physiology, would prevent TBI-induced sleep dysfunction and alter sleep-modulatory peptide expression. In contrast to our hypothesis, the mild, repeated head injury that we used did not significantly alter basal or homeostatic sleep responses in mice housed in standard laboratory conditions. Sham-injured mice housed in enriched environments exhibited enhanced rapid eye movement (REM) sleep and expression of the REM-promoting peptide pro-melanin-concentrating hormone, an effect that was not apparent in TBI mice housed in enriched environments. Thus, TBI blocked the REM-enhancing effects of EE. This work has important implications for the management and rehabilitation of the TBI patient population.

Alcohol Use Disorder and Traumatic Brain Injury

Alcohol use and traumatic brain injury (TBI) are inextricably and bidirectionally linked. Alcohol intoxication is one of the strongest predictors of TBI, and a substantial proportion of TBIs occur in intoxicated individuals. An inverse relationship is also emerging, such that TBI can serve as a risk factor for, or modulate the course of, alcohol use disorder (AUD). Critically, alcohol use after TBI is a key predictor of rehabilitation outcomes, prognosis, and additional head injuries. This review provides a general overview of the bidirectional relationship between TBI and AUD and a discussion of potential neuropsychological and neurobiological mechanisms that might underlie the relationship.