Endocannabinoid signaling regulates post-operative delirium through glutamatergic mediodorsal thalamus-prelimbic prefrontal cortical projection

Lipopolysaccharide-Induced Delirium-Like Behavior and Microglial Activation in Mice Correlate With Bispectral Electroencephalography

Delirium is a multifactorial medical condition characterized by impairment across various mental functions and is one of the greatest risk factors for prolonged hospitalization, morbidity, and mortality. Research focused on delirium has proven to be challenging due to a lack of objective measures for diagnosing patients, and few laboratory models have been validated. Our recent studies report the efficacy of bispectral electroencephalography (BSEEG) in diagnosing delirium in patients and predicting patient outcomes. We applied BSEEG to validate a lipopolysaccharide-induced mouse model of delirium. Moreover, we investigated the relationship between BSEEG score, delirium-like behaviors, and microglia activation in hippocampal dentate gyrus and cortex regions in young and aged mice. There was a significant correlation between BSEEG score and impairment of attention in young mice. Additionally, there was a significant correlation between BSEEG score and microglial activation in hippocampal dentate gyrus and cortex regions in young and aged mice. We have successfully validated the BSEEG method by showing its associations with a level of behavioral change and microglial activation in an lipopolysaccharide-induced mouse model of delirium. In addition, the BSEEG method was able to sensitively capture an lipopolysaccharide-induced delirium-like condition that behavioral tests could not capture because of a hypoactive state.

Myogenic Classical Endocannabinoids, Their Targets and Activity

This review focuses on the recently discovered specific action of two classical endocannabinoids (ECs), 2-arachidonoylglycerol (2-AG) and arachidonoyl ethanolamide (AEA), in the case of their synthesis and degradation in skeletal muscles; in other words, this review is dedicated to properties and action of the myoendocannabinoid (myoEC) pool. Influence of this pool is considered at three different levels: at the level of skeletal muscles, motor synapses, and also at the level of the whole organism, including central nervous system. Special attention is paid to the still significantly underestimated and intriguing ability of ECs to have positive effect on energy exchange and contractile activity of muscle fibers, as well as on transmitter secretion in motor synapses. Role of muscle contractions in regulation of activity balance between the enzymes catalyzing synthesis and degradation of myoECs and, therefore, in the release of myoECs and exertion of their specific effects is thoroughly considered. Increasingly popular hypotheses about the prominent role of myoECs (AEA and/or 2-AG) in the rise of the overall level of ECs in the blood during muscle exercise and the development of "runner's high" and about the role of myoECs in the correction of a number of psychophysiological conditions (pain syndrome, stress, etc.) are discussed here. Thus, this review presents information about the myoEC pool from a totally new viewpoint, underlining its possible independent and non-trivial regulatory role in the body, in contrast to the traditional and well-known activity of neurogenic ECs.

Drugs, Delirium, and Trauma: Substance Use and Incidence of Delirium After Traumatic Brain Injury

INTRODUCTION

There is a paucity of data on the effect of preinjury substance (alcohol, drugs) abuse on the risk of delirium in patients with traumatic brain injury (TBI). This study aimed to assess the incidence of delirium among patients with blunt TBI in association with different substances.

METHODS

We analyzed the 2020 American College of Surgeons-Trauma Quality Improvement Program. We included all adult (≥18 y) patients with blunt TBI who had a recorded substance (drugs and alcohol) screening. Our primary outcome was the incidence of delirium.

RESULTS

A total of 72,901 blunt TBI patients were identified. The mean (standard deviation) age was 56 (20) years and 68.0% were males. The median (interquartile range) injury severity score was 17 (10-25). Among the study population, 23.1% tested positive for drugs (Stimulants: 3.0%; Depressants: 2.9%, hallucinogens: 5.1%, Cannabinoids: 13.4%, TCAs: 0.1%), and 22.8% tested positive for Alcohol. Overall, 1856 (2.5%) experienced delirium. On univariate analysis, patients who developed delirium were more likely to have positive drug screening results. On multivariable regression analyses, positive screen tests for isolated stimulants (adjusted odds ratio [aOR]: 1.340, P = 0.018), tricyclic antidepressants (aOR: 3.107, P = 0.019), and cannabinoids (aOR: 1.326, P ≤ 0.001) were independently associated with higher odds of developing delirium.

CONCLUSIONS

Nearly one-fourth of adult patients with blunt TBI had an initial positive substance screening test. Patients with positive results for isolated stimulants, tricyclic antidepressants, and cannabinoids were at a higher risk of developing delirium, whereas this association was not evident with other drugs and alcohol-positive tests. These findings emphasize the need for early drug screening in TBI patients and close monitoring of patients with positive screening tests.

BLA-involved circuits in neuropsychiatric disorders

The basolateral amygdala (BLA) is the subregion of the amygdala located in the medial of the temporal lobe, which is connected with a wide range of brain regions to achieve diverse functions. Recently, an increasing number of studies have focused on the participation of the BLA in many neuropsychiatric disorders from the neural circuit perspective, aided by the rapid development of viral tracing methods and increasingly specific neural modulation technologies. However, how to translate this circuit-level preclinical intervention into clinical treatment using noninvasive or minor invasive manipulations to benefit patients struggling with neuropsychiatric disorders is still an inevitable question to be considered. In this review, we summarized the role of BLA-involved circuits in neuropsychiatric disorders including Alzheimer's disease, perioperative neurocognitive disorders, schizophrenia, anxiety disorders, depressive disorders, posttraumatic stress disorders, autism spectrum disorders, and pain-associative affective states and cognitive dysfunctions. Additionally, we provide insights into future directions and challenges for clinical translation.

Chronic exposure to PM10 induces anxiety-like behavior via exacerbating hippocampal oxidative stress

As one of the most environmental concerns, inhaled particulate matter (PM10) causes numerous health problems. However, the associations between anxiety behavior and toxicity caused by PM10 have rarely been reported so far. To investigate the changes of behavior after PM10 exposure and to identify the potential mechanisms of toxicity, PM10 samples (with doses of 15 mg/kg and 30 mg/kg) were intratracheally instilled into rats to simulate inhalation of polluted air by the lungs. After instillation for eight weeks, anxiety-like behavior was evaluated, levels of oxidative stress and morphological changes of hippocampus were measured. The behavioral results indicated that PM10 exposure induced obvious anxiety-like behavior in the open field and elevated plus maze tests. Both PM10 concentrations tested could increase whole blood viscosity and trigger hippocampal neuronal damage and oxidative stress by increasing superoxide dismutase (SOD) activities and malondialdehyde levels, and decreasing the expressions of antioxidant-related proteins (e.g., nuclear factor erythroid 2-related factor 2 (Nrf2), SOD1 and heme oxygenase 1). Furthermore, through collecting and analyzing questionnaires, the data showed that the participants experienced obvious anxiety-related emotions and negative somatic responses under heavily polluted environments, especially PM10 being the main pollutant. These results show that PM10 exposure induces anxiety-like behavior, which may be related to suppressing the Nrf2/Keap1-SOD1 pathway.