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

Area of Science:

• Neuroscience
• Pharmacology
• Neurochemistry

Background:

• Met-enkephalin immunoreactive material (ME-IR) plays a role in regulating neurotransmission.
• Psychostimulants like amphetamine are known to affect dopamine pathways.
• Fipexide is a psychostimulant with mild dopaminomimetic activity.

Purpose of the Study:

• To investigate the effect of amphetamine and fipexide on ME-IR release from rat striatal slices.
• To determine if these effects differ between in vitro and in vivo administration.
• To explore the mechanism underlying fipexide's action on dopamine neurotransmission.

Main Methods:

• In vitro studies using rat striatal slices to measure ME-IR release.
• In vivo acute and chronic administration of amphetamine and fipexide.
• Reserpine pretreatment to assess the role of catecholamines.

Main Results:

• Both amphetamine and fipexide significantly inhibited ME-IR release in vitro.
• This inhibitory effect was consistent with both acute and chronic in vivo administration.
• The action of both drugs persisted after reserpine pretreatment, indicating a non-catecholaminergic mechanism.

Conclusions:

• Fipexide, similar to amphetamine, inhibits ME-IR release.
• This inhibition suggests that fipexide may facilitate dopamine neurotransmission.
• The mechanism likely involves the disinhibition of an enkephalinergic inhibitory feedback circuit.