Changes in turnover of cerebral monoamines following inhibition of enkephalin metabolism by thiorphan and bestatin.

Thiorphan, an 'enkephalinase' inhibitor, and bestatin, an aminopeptidase inhibitor, decreased the turnover of noradrenaline and increased that of dopamine and serotonin in mouse brain regions. All effects were prevented by naloxone, indicating that when protected from the action of inactivating neuropeptidases endogenous enkephalins might affect monoaminergic neurons in the same way as exogenous opiates.