From chronic stress and anxiety to neurodegeneration: Focus on neuromodulation of the axon initial segment

Jelena Radulovic, Sanja Ivkovic, Miroslav Adzic

Research output: Chapter in Book/Report/Conference proceedingChapter

Abstract

To adapt to the sustained demands of chronic stress, discrete brain circuits undergo structural and functional changes often resulting in anxiety disorders. In some individuals, anxiety disorders precede the development of motor symptoms of Parkinson's disease (PD) caused by degeneration of neurons in the substantia nigra (SN). Here, we present a circuit framework for probing a causal link between chronic stress, anxiety, and PD, which postulates a central role of abnormal neuromodulation of the SN's axon initial segment by brainstem inputs. It is grounded in findings demonstrating that the earliest PD pathologies occur in the stress-responsive, emotion regulation network of the brainstem, which provides the SN with dense aminergic and cholinergic innervation. SN's axon initial segment (AIS) has unique features that support the sustained and bidirectional propagation of activity in response to synaptic inputs. It is therefore, especially sensitive to circuit-mediated stress-induced imbalance of neuromodulation, and thus a plausible initiating site of neurodegeneration. This could explain why, although secondary to pathophysiologies in other brainstem nuclei, SN degeneration is the most extensive. Consequently, the cardinal symptom of PD, severe motor deficits, arise from degeneration of the nigrostriatal pathway rather than other brainstem nuclei. Understanding when and how circuit dysfunctions underlying anxiety can progress to neurodegeneration, raises the prospect of timed interventions for reversing, or at least impeding, the early pathophysiologies that lead to PD and possibly other neurodegenerative disorders.

Original languageEnglish (US)
Title of host publicationHandbook of Clinical Neurology
PublisherElsevier B.V.
Pages481-495
Number of pages15
DOIs
StatePublished - Jan 2022

Publication series

NameHandbook of Clinical Neurology
Volume184
ISSN (Print)0072-9752
ISSN (Electronic)2212-4152

Keywords

  • Anxiety
  • Axon initial segment
  • Neurodegeneration
  • Neuromodulation
  • Parkinson's disease

ASJC Scopus subject areas

  • Neurology
  • Clinical Neurology

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