Prior behavioral experience can reverse the effects of morphine.

Area of Science:

• Behavioral pharmacology
• Animal behavior studies
• Neuroscience

Background:

• Morphine is known to decrease avoidance responding in trained animals.
• The influence of prior behavioral experience on drug effects is not fully understood.

Purpose of the Study:

• To investigate how environmental conditions alter the behavioral effects of morphine.
• To determine if prior exposure to shock-maintained behavior modifies morphine's impact on avoidance responding.

Main Methods:

• Squirrel monkeys were trained to perform avoidance responding.
• Animals were exposed to different conditions: concurrent or prior shock-maintained responding.
• The effects of morphine administration on avoidance responding were measured.

Main Results:

• Morphine typically decreased avoidance responding.
• This rate-decreasing effect was reversed in animals with prior or concurrent exposure to shock-maintained responding.
• Behavioral experience significantly modulated morphine's effects.

Conclusions:

• Environmental conditions and behavioral experience are critical factors in determining drug effects.
• Specific environmental contexts can completely reverse the typical pharmacological actions of morphine on behavior.