[Inhibition of the evoked liberation of (Met5)enkephalin from slices of globus pallidus in the presence of thiorphan and bestatin].

(Met5) enkephalin released from slices of Rat globus pallidus by 30 mM or 50 mM K+ is hydrolysed to the extent of 85% before reaching the incubation medium. When thiorphan and bestatin, two peptidase inhibitors, are added, this inactivation process is completely prevented but the peptide release from tissues is significantly diminished. The latter effect being reversed in the presence of an opioid antagonist, naloxone, in moderate concentration, the existence of an auto-inhibition process regulating enkephalin release is suggested.