Scientific rationale for the use of α2A-adrenoceptor agonists in treating neuroinflammatory cognitive disorders

Stress and inflammation target dorsolateral prefrontal cortex function: Neural mechanisms underlying weakened cognitive control

Most mental disorders involve dysfunction of the dorsolateral prefrontal cortex (dlPFC), a recently evolved brain region that subserves working memory, abstraction and the thoughtful regulation of attention, action and emotion. For example, schizophrenia, depression, long-COVID and Alzheimer's disease are all associated with dlPFC dysfunction, with neuropathology often focused in layer III. The dlPFC has extensive top-down projections: e.g. to the posterior association cortices to regulate attention, and the subgenual cingulate cortex via the rostral and medial PFC to regulate emotional responses. However, the dlPFC is particularly dependent on arousal state, and is very vulnerable to stress and inflammation, which are etiological and/or exacerbating factors in most mental disorders. The cellular mechanisms by which stress and inflammation impact the dlPFC are a topic of current research, and are summarized in this review. For example, the layer III dlPFC circuits generating working memory-related neuronal firing have unusual neurotransmission, depending on NMDAR and nicotinic-α7R actions that are blocked under inflammatory conditions by kynurenic acid. These circuits also have unusual neuromodulation, with the molecular machinery to magnify calcium signaling in spines needed to support persistent firing, which must be tightly regulated to prevent toxic calcium actions. Stress rapidly weakens layer III connectivity by driving feedforward calcium-cAMP opening of potassium channels on spines. This is regulated by postsynaptic noradrenergic α2A-AR and mGluR3 signaling, but dysregulated by inflammation and/or chronic stress exposure, contributing to spine loss. Treatments that strengthen dlPFC, via pharmacological (the α2A-AR agonist, guanfacine) or rTMS manipulation, provide a rational basis for therapy.

Evaluation and Pharmacologic Management of Paroxysmal Sympathetic Hyperactivity in Traumatic Brain Injury

OBJECTIVE

Paroxysmal sympathetic hyperactivity (PSH) can occur in up to 10% of severe traumatic brain injury (TBI) patients and is associated with poorer outcomes. A consensus regarding management is lacking. We provide a practical guide on the multi-faceted clinical management of PSH, including pharmacological, procedural and non-pharmacological interventions. In addition to utilizing a standardized assessment tool, the use of medications to manage sympathetic and musculoskeletal manifestations (including pain) is highlighted. Recent studies investigating new approaches to clinical management are included in this review of pharmacologic treatment options.

CONCLUSION

While studies regarding pharmacologic selection for PSH are limited, this paper suggests a clinical approach to interventions based on predominant symptom presentation (sympathetic hyperactivity, pain and/or muscle hypertonicity) and relevant medication side effects.

Unraveling Links between Chronic Inflammation and Long COVID: Workshop Report

As COVID-19 continues, an increasing number of patients develop long COVID symptoms varying in severity that last for weeks, months, or longer. Symptoms commonly include lingering loss of smell and taste, hearing loss, extreme fatigue, and "brain fog." Still, persistent cardiovascular and respiratory problems, muscle weakness, and neurologic issues have also been documented. A major problem is the lack of clear guidelines for diagnosing long COVID. Although some studies suggest that long COVID is due to prolonged inflammation after SARS-CoV-2 infection, the underlying mechanisms remain unclear. The broad range of COVID-19's bodily effects and responses after initial viral infection are also poorly understood. This workshop brought together multidisciplinary experts to showcase and discuss the latest research on long COVID and chronic inflammation that might be associated with the persistent sequelae following COVID-19 infection.