Acute and repeated administration of sulpiride alters Met-and Leu-enkephalin content of rat brain.

Following acute administration of sulpiride (100 mg/kg, i.p.), Met-enkephalin levels were increased in striatum but decreased in substantia nigra and nucleus accumbens. No effect was observed in hypothalamus or frontal cortex. In contrast, Leu-enkephalin content was decreased in the nucleus accumbens but not elsewhere. Administration of sulpiride (10 or 100 mg/kg, i.p.) for 21 days, followed by 2 days drug withdrawal, caused a dose-dependent increase in Met-enkephalin in nucleus accumbens but decreases in hypothalamus and frontal cortex. No change was observed in the striatum or substantia nigra. Repeated sulpiride administration caused a decrease in Leu-enkephalin content of the hypothalamus and cortex but not elsewhere.