Chronic phencyclidine increases methionine-enkephalin level in mouse striatum.

The chronic administration of phencyclidine-HCl (PCP-HCl), 10 mg/kg, for 6-7 days resulted in a significant increase in the striatal methionine-enkephalin level, although acute administration induced no change of methionine-enkephalin level in this area. The methionine-enkephalin levels in other areas investigated, i.e. the medulla oblongata/pons, the midbrain, the hypothalamus and the cortex, were unchanged after chronic PCP treatment. These results suggest that chronic administration of PCP alters the enkephalinergic neuronal activity in the striatum.