β‐Endorphin‐(1–27) inhibits the spinal beta‐endorphin‐induced release of Met‐enkephalin

Abstract

The effect of intraventricular .beta.-endorphin-(1-27) on the spinal release of Met-enkephalin induced by intraventricular .beta.-endorphin was studied using the intrathecal superfusion technique in urethane anesthetized rats. Intraventricular injection of .beta.-endorphin at a dose of 15 .mu.g released Met-enkephalin from the spinal cord. This release of Met-enkephalin induced by .beta.-endorphin was significantly reduced by .beta.-endorphin-(1-27), 60 .mu.g, injected intraventricularly. Injection of .beta.-endorphin (1-27) itself did not cause any release of Met-enkephalin. The finding is in line with the previous report the .beta.-endorphin (1-27) inhibited the analgesia induced by .beta.-endorphin.