Only arginine vasopressin, not oxytocin and endogenous opiate peptides, in hypothalamic paraventricular nucleus play a role in acupuncture analgesia in the rat

Our previous study proved that hypothalamic paraventricular nucleus (PVH) plays an important role in acupuncture analgesia. The effect of acupuncture on the concentrations of arginine vasopressin (AVP), oxytocin (OXT), leucine-enkephaline (L-Ek), β-endorphin (β-Ep) and dynorphinA1–13 (DynA1–13) was investigated in rat PVH. Electrical acupuncture of “Zusanli” points (St. 36) 30 min increased the AVP, not OXT, L-Ek, β-Ep and DynA1–13 concentrations in PVH tissue using micropunch and radioimmunoassay, which showed a negative relationship between the pain threshold and AVP concentrations in PVH tissue. Electrical acupuncture could elevate the AVP concentrations in PVH perfuse liquid during acupuncture, and then reduce the AVP concentrations in PVH perfuse liquid after acupuncture. But no change in OXT, L-Ek, β-Ep and DynA1–13 concentrations was detected in PVH perfuse liquid. Electrical acupuncture decreased the number of AVP, not OXT, L-Ek, β-Ep and DynA1–13 immunoreactive cells in PVH using immunocytochemistry. The results suggested that only AVP, not OXT and endogenous opiate peptides in PVH involved acupuncture analgesia in the rat.