Study design: The effect of oxytocin on low back pain in patients and its mechanism in rats were investigated.
Methods: Intrathecal injection, radioimmunoassay, and potassium iontophoresis tail-flick test were used to investigate the effect of oxytocin.
Results: In humans, acute and chronic low back pain causes a marked change of oxytocin content within cerebral spinal fluid and plasma; oxytocin relieves low back pain (ED50 0.172 in chronic and 0.121 micrograms/kg in acute). In rats, oxytocin had a dose-related analgesic effect (ED50 0.067 micrograms/kg). At high levels, oxytocin induced locomotor ataxia (ED50 17.915 micrograms/kg) and death (LD50 27.224 micrograms/kg). Oxytocin antagonist [d(CH2)5, Tyr(Me)2, Orn8]-vasotocin and opiate receptor-blocker naloxone could reverse oxytocin-induced analgesia. Oxytocin also increased beta-endorphin, L-encephalin, and dynorphin A1-13 contents in the spinal cord, whereas oxytocin antagonist caused a decrease.
Conclusions: These results suggest that oxytocin induces analgesia in low back pain involving the endogenous opiate peptide system and may be effective and safe in acute and chronic low back pain.