Intrathecal administration of oxytocin induces analgesia in low back pain involving the endogenous opiate peptide system.

METHODS

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.