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upstart writes in with an IRC submission:

New mechanism of pain control revealed:

Found in the outer two layers of gray matter near the back of the spinal cord -- a location referred to as the superficial laminae of the spinal dorsal horn -- the astrocytes are in a region known to carry general sensory information such as pressure, pain, and heat from around the body to the brain.

[...] Using mice, the researchers showed that stimulating noradrenergic (NAergic) neurons -- so called for their use of noradrenaline as a neurotransmitter -- that carry signals from the locus coeruleus (LC) in the brain down to the spinal dorsal horn activates the astrocytes and that the astrocyte activation results in pain hypersensitivity.

These observations overturn the prevailing view that descending LC-NAergic neurons suppress pain transmission in the spinal dorsal horn.

[...] To initially test this, the researchers genetically engineered mice in which response of astrocytes to noradrenaline was selectively inhibited and gave them duloxetine, an analgesic drug thought to increase levels of noradrenaline in the spinal cord by preventing uptake by descending LC-NAergic neurons.

Indeed, the modified mice exhibited an enhanced easing of chronic pain by duloxetine, further supporting the researchers' proposed role of the astrocytes.

[*] Glial cells.

Journal Reference:
Yuta Kohro, Tsuyoshi Matsuda, Kohei Yoshihara, et al. Spinal astrocytes in superficial laminae gate brainstem descending control of mechanosensory hypersensitivity, Nature Neuroscience (DOI: 10.1038/s41593-020-00713-4)

Original Submission