P2X3 receptors in the paraventricular hypothalamus: a specific target for visceral pain.

In a recent article published in Neuron, Li et al. (Neuron 112(22):3734-3749.e5, 2024) accomplished a major scientific advance by reporting that ATP-sensitive P2X3 receptor-channels (P2X3Rs) in the paraventricular hypothalamus (PVH) specifically regulate visceral pain without affecting somatic pain. On the other hand, vasoactive intestinal polypeptide-sensing receptors (VIPR2) selectively process somatic pain without altering visceral pain. Function-dependent laser capture microdissection sequencing (fLCM-Seq) and immunohistochemistry demonstrated that P2X3Rs and VIPR2 have different transcriptional profiles and belong to the colorectal distension (CRD) and von Frey filament (VFF)-stimulated subgroups of PVH neurons, respectively. An anterograde tracing strategy, in which green fluorescent protein (GFP) was selectively expressed in CRD-labeled or VFF-labeled PVH neurons, showed that PVH^P2X3R+ neuronal projections terminated exclusively at the ventral part of the lateral septal nucleus (LSV) while the PVH^VIPR2+ neuronal projections terminated at the caudal part of the zona incerta (ZIC). The PVH^P2X3R+ circuit selectively responded to visceral pain while remaining unresponsive to somatic pain. By contrast, the PVH^VIPR2+ circuit selectively responded to somatic pain, while it did not react to visceral pain. Knockdown of P2X3R expression in PVH neurons enhanced the visceral pain threshold without affecting somatic nociception, and the reverse findings were true for the knockdown of the VIPR2 expressing PVH neurons. All these results provide possible new strategies based on central-targeted therapies for the future treatment of visceral and somatic pain, respectively.