Release of met-enkephalin from rat striatal slices: effect of amphetamine and fipexide.

The release of Met-enkephalin immunoreactive material (ME-IR) from rat striatal slices is affected by exposure to amphetamine and fipexide (chloro-4-phenoxy)-2-acetyl-1-(methylene-dioxy 3, 4-benzyl-4-piperazine) a psychostimulant drug with mild dopaminomimetic activity. Both amphetamine and fipexide inhibited in vitro the release of ME-IR. The same effect was observed after in vivo acute administration and is also maintained after chronic treatment. The action of fipexide and amphetamine is still present after reserpine pretreatment. The results indicate that fipexide may facilitate dopamine neurotransmission by inhibition of an enkephalinergic inhibitory feed-back circuit.