The levels of three aminopeptidase activities involved in the degradation of enkephalins (soluble, M and MII) in several rat brain areas were studied after lidocaine administration. 2. Soluble aminopeptidase activity showed decreases in the frontal cortex and in the pituitary gland after treatment. 3. No significant changes in the complete membrane-bound aminopeptidase activity were appreciated in any other of the brain areas. 4. However, decreases of the membrane-bound puromycin-insensitive aminopeptidase activity in the frontal cortex, the hippocampus and the thalamus, after lidocaine administration, were observed.
