Persistent augmented dopamine release after acute cocaine requires dopamine receptor activation

Area of Science:

• Neuroscience
• Pharmacology
• Neurochemistry

Background:

• Cocaine, a psychostimulant, affects the nigrostriatal dopamine system.
• Cocaine blocks dopamine uptake and acts as a local anesthetic.
• Previous studies show cocaine alters dopamine release dynamics.

Purpose of the Study:

• To determine which action of cocaine causes persistent augmentation of amphetamine-induced dopamine release.
• To investigate the role of dopamine uptake blockade and receptor stimulation in this phenomenon.
• To elucidate the specific dopamine receptor subtypes involved.

Main Methods:

• Rats were pretreated with cocaine or other drugs.
• Dopamine release was measured in vitro using striatal slice preparations.
• Drugs with varying mechanisms of action (uptake blockade, receptor agonism, local anesthesia) were used.
• Dopamine receptor antagonists (nonselective, D-1, D-2) were employed to block cocaine's effects.

Main Results:

• A single cocaine injection led to persistent augmentation of amphetamine-stimulated [3H]dopamine release.
• Mazindol (dopamine uptake blocker) and apomorphine (dopamine receptor agonist) also augmented release.
• Lidocaine (local anesthetic) had no effect on dopamine release.
• Pretreatment with dopamine receptor antagonists blocked the long-lasting augmentation of release.

Conclusions:

• Cocaine's persistent augmentation of dopamine release is primarily mediated by indirect activation of dopamine receptors.
• Both D-1 and D-2 dopamine receptor subtypes are involved in this cocaine-induced effect.
• Dopamine uptake blockade and subsequent receptor stimulation are key mechanisms, not local anesthesia.