locus ceruleus (locus ferrugineus, substantia ferruginea, locus cinereus)

Function

• role in physiologic response to stress & panic

Structure

• the locus ceruleus is a shallow depression, blue in a fresh-cut brain, near the lateral wall of the fourth ventricle & cerebral aqueduct
• it consists of about 20,000 melanin-pigmented neuronal cell bodies with norepinephrine-containing axons

Afferents

• medial prefrontal cortex
• nucleus paragigantocellularis, which integrates autonomic & environmental stimuli
• nucleus prepositus hypoglossi, involved in gaze
• lateral hypothalamus, which releases orexin, excitatory in the locus coeruleus

Efferents

• projects widely to the spinal cord, amygdala, hypothalamus, striatum, cerebral cortex & cerebellum

Pathology

• the locus ceruleus may be earliest affected region in Alzheimer's disease
  • abnormal tau aggregates (pretangles) develop within proximal axons of noradrenergic locus coeruleus projection neurons in the absence of tau lesions (pretangles, NFTs) in the entorhinal cortex or beta-amyloid pathology in the neocortex
  • AD may begin in the locus ceruleus & progress to the entorhinal cortex via trans-synaptic transport of tau protein aggregates & neuron-to-neuron transmission
  • a prion-like mechanism is suggested

More general terms

• CNS nucleus

Component of

• mesencephalon (midbrain)
• pons