Can you train the locus coeruleus to fire less aggressively?

Indirectly, yes. The LC receives inhibitory input from sources that respond to behavioral training: vagal tone (improved by extended-exhale breathing and aerobic exercise), GABAergic projections from the prefrontal cortex (strengthened by meditation and cognitive reappraisal), and orexin signaling regulated by sleep consistency. Measurable reductions in phasic overshoot have been documented in 8-week mindfulness and aerobic training studies using physiological arousal markers as proxies for LC activity.

Why does prazosin help PTSD nightmares specifically?

Prazosin blocks alpha-1 adrenergic receptors in the brain. During REM sleep, the LC reactivates and releases norepinephrine that consolidates traumatic memory traces. When alpha-1 receptors in the amygdala are blocked, the fear-memory consolidation signal cannot land and nightmare frequency drops. A 2007 RCT by Raskind et al. (VA Puget Sound) showed significant nightmare reduction at 1 to 4 mg nightly.

Does locus coeruleus dysfunction cause anxiety, or does anxiety cause LC dysfunction?

Both directions are operative. Chronic stress sensitizes LC autoreceptors over time, lowering the threshold for hyperreactivity. Once sensitized, the LC amplifies responses to stimuli that would not previously trigger a full alarm. This loop is why untreated anxiety disorders tend to worsen rather than self-resolve. The NIH NINDS identifies norepinephrine dysregulation as a key mechanism in stress-related neurological vulnerability.

What depletes norepinephrine over time?

Sustained psychological stress is the primary driver: chronically high demand for norepinephrine output eventually exceeds the LC's synthetic capacity. Chronic sleep deprivation reduces tyrosine hydroxylase activity. Severe caloric restriction limits precursor availability. The clinical presentation of norepinephrine depletion includes fatigue, poor concentration, emotional flatness, and orthostatic hypotension, symptoms often misread as depression.