The locus coeruleus in aging and neurodegenerative diseases

The locus coeruleus (LC), a prominent neuromelanin-containing nucleus, plays a critical role in the central nervous system by serving as the main source of norepinephrine. First described by Félix Vicq d’Azyr in the 18th century and later identified as a noradrenaline-rich region through fluorescence histochemistry in the 1960s, the LC influences various brain functions, including attention, learning, stress responses, pain modulation, memory, and sleep. This review explores the anatomy, morphology, and neurochemistry of LC neurons, emphasizing their projections and interactions with multiple brain regions such as the cortex, hippocampus, and thalamus. Additionally, we examine the involvement of the LC in the pathophysiology of age-related neurodegenerative diseases, including Alzheimer’s and Parkinson’s diseases, where significant neuronal loss in the LC correlates with cognitive decline and other clinical symptoms. Understanding the anatomical and functional heterogeneity of LC neurons provides insights into their crucial role in neuromodulation and highlights potential therapeutic targets for neurodegenerative disorders.