Laminar-selective spinal astrocyte population capable of converting tactile information into nociceptive in rats.

We previously identified a spinal astrocyte population that expresses hairy and enhancer of split 5 (Hes5) and is selectively present in superficial laminae in mice. However, it was unclear whether such astrocyte heterogeneity is commonly observed across species. Using adeno-associated viral (AAV) vectors incorporating a rat Hes5 promotor (AAV-Hes5P), we found that AAV-Hes5P-captured astrocytes were selectively located in the superficial laminae in rats.

Identification of Spinal Inhibitory Interneurons Required for Attenuating Effect of Duloxetine on Neuropathic Allodynia-like Signs in Rats.

Neuropathic pain is a chronic pain condition that occurs after nerve damage; allodynia, which refers to pain caused by generally innocuous stimuli, is a hallmark symptom. Although allodynia is often resistant to analgesics, the antidepressant duloxetine has been used as an effective therapeutic option. Duloxetine increases spinal noradrenaline (NA) levels by inhibiting its transporter at NAergic terminals in the spinal dorsal horn (SDH), which has been proposed to contribute to its pain-relieving effect.

Selective Involvement of a Subset of Spinal Dorsal Horn Neurons Operated by a Prodynorphin Promoter in Aβ Fiber-Mediated Neuropathic Allodynia-Like Behavioral Responses in Rats.

Mechanical allodynia (pain produced by innocuous stimuli such as touch) is the main symptom of neuropathic pain. Its underlying mechanism remains to be elucidated, but peripheral nerve injury (PNI)-induced malfunction of neuronal circuits in the central nervous system, including the spinal dorsal horn (SDH), is thought to be involved in touch-pain conversion. Here, we found that intra-SDH injection of adeno-associated viral vectors including a prodynorphin promoter (AAV-PdynP) captured a subset of neurons that were mainly located in the superficial laminae, including lamina I, and exhibited mostly inhibitory characteristics.

Improvement of the affinity of an anti-rat P2X4 receptor antibody by introducing electrostatic interactions.

We have recently developed a mouse monoclonal antibody (12-10H) binding to the head domain region in rat P2X4 receptor (rP2X4R, which is crucial for the pathogenesis of neuropathic pain) expressed on the cell with the highest binding affinity (K = 20 nM). However, the 12-10H antibody failed to detect endogenously expressed P2X4Rs in microglia isolated from the spinal cord of rats whose spinal nerves were injured. Then, we prepared R5 mutant, in which five arginine residues were introduced into variable regions except for the "hot spot" in the 12-10H antibody to increase electrostatic interactions with the head domain, an anionic region, in rP2X4R.

A subset of spinal dorsal horn interneurons crucial for gating touch-evoked pain-like behavior.

A cardinal, intractable symptom of neuropathic pain is mechanical allodynia, pain caused by innocuous stimuli via low-threshold mechanoreceptors such as Aβ fibers. However, the mechanism by which Aβ fiber-derived signals are converted to pain remains incompletely understood. Here we identify a subset of inhibitory interneurons in the spinal dorsal horn (SDH) operated by adeno-associated viral vectors incorporating a neuropeptide Y promoter (AAV-NpyP) and show that specific ablation or silencing of AAV-NpyP SDH interneurons converted touch-sensing Aβ fiber-derived signals to morphine-resistant pain-like behavioral responses.