Rats choose cocaine over dopamine agonists in a two-lever self-administration preference test.

Area of Science:

• Neuroscience
• Pharmacology
• Behavioral Science

Background:

• Rats self-administer dopamine D(1) and D(2) agonists, alone or in combination.
• D(1):D(2) agonist combinations mimic cocaine's response patterns.
• The reinforcing effects of dopamine agonists compared to cocaine require further investigation.

Purpose of the Study:

• To determine if rats prefer cocaine over individual dopamine D(1) or D(2) agonists.
• To assess preference between cocaine and combined D(1):D(2) dopamine agonist mixtures.
• To compare the reinforcing strength of cocaine and dopamine agonists.

Main Methods:

• Rats were trained in a two-lever choice task.
• Cocaine was paired against itself at different doses or against dopamine agonists (D(1) or D(2)) or agonist combinations.
• Preference was measured by lever choices under fixed-ratio schedules.

Main Results:

• Rats preferred higher doses of cocaine over lower doses.
• Rats preferred cocaine (800 microg/kg) over individual D(1) or D(2) dopamine agonists.
• No preference was observed between 800 microg/kg cocaine and D(1):D(2) agonist mixtures.
• A high-dose D(1):D(2) agonist mixture was preferred over a low dose of cocaine.

Conclusions:

• Dopamine D(1) and D(2) agonists alone do not fully replicate cocaine's reinforcing effects.
• Combinations of D(1) and D(2) dopamine agonists may approximate the reinforcing strength of cocaine.
• These findings contribute to understanding the neurochemical basis of drug reinforcement.