A lever without a pill: the vagus and the locus coeruleus
If the problem is a shortage of central norepinephrine, one obvious question is whether you can raise it without a drug. There is a plausible route: the vagus nerve.
Vagal afferents carry signals from the body to the brainstem nucleus of the solitary tract, which projects to the locus coeruleus — the brain’s main norepinephrine nucleus. Transcutaneous auricular vagus nerve stimulation (taVNS) applies a small electrical signal to the ear, and reviews describe it as activating this locus-coeruleus-norepinephrine pathway (Hilz (2022)). In mice, taVNS activated norepinephrine-producing (tyrosine-hydroxylase-positive) neurons in the locus coeruleus, and those neurons mediated the treatment’s effects (Lv et al. (2024)).
Why this is attractive. Unlike stimulants, taVNS does not push the system with a drug, is reversible, and can be dose-controlled. If it works, it is also a probe: a safe way to test whether raising norepinephrine changes anything measurable.
The limits. The human evidence is at review level; the direct mechanistic evidence is in mice; and ME/CFS-specific data are preliminary. And a key caveat runs through the whole series: the underlying deficit itself is unreplicated.
How we would know. A trial could ask whether taVNS changes a non-invasive norepinephrine readout — pupil measures, handgrip endurance, a urine ratio — and, if the clearance loop is real, whether it changes a clearance or inflammatory marker. If it moves nothing, the non-drug route is unlikely to matter.
Not a recommendation — a testable idea.