An inhibitor of opioid peptide degradation produces analgesia in mice.

Bacitracin, a known inhibitor of brain peptidases which degrade the enkephalins and endorphins, produced dose-dependent analgesia in mice when injected into the lateral ventricle of the brain as determined by the tail-flick assay. The analgesic response peaked at 15 min post-injection but was reduced to control levels by 3.5 hours. Naloxone reversed the analgesic response to bacitracin, suggesting that opiate receptors may be involved. It is proposed that bacitracin produces analgesia by preventing the enzymatic destruction of endogenously released opioid peptides.