Oxytocin in rat nucleus raphe magnus influences pain modulation

The main function of Nucleus raphe magnus (NRM) is mostly pain mediation. Our previous study has demonstrated that oxytocin (OXT) regulates antinociception through the central nervous system rather than the peripheral organs, and pain stimulation increases OXT concentration in the NRM. The experiment was designed to investigate OXT in the rat NRM effect on pain modulation. The results showed that 1) pain stimulation increased OXT concentration in NRM perfusion liquid; 2) Intra-NRM microinjection of OXT increased the pain threshold in a dose-dependent manner, whereas intra-NRM microinjection of OXT receptor antagonist, desGly-NH2, d(CH2)5[D-Tyr2, Thr-sup-4]OVT decreased the pain threshold; 3) NRM pre-treatment with OXT receptor antagonist completely attenuated the pain threshold increase induced by intra-NRM administration of OXT. The data suggested that OXT in NRM was involved in antinociception via OXT receptors.