Effects of chronically administered d-amphetamine on spaced responding maintained under multiple and single-component...

Area of Science:

• Behavioral pharmacology
• Animal behavior studies

Background:

• Operant conditioning principles in animal research.
• D-amphetamine's known psychostimulant effects.

Purpose of the Study:

• Investigate d-amphetamine's effects on rat responding under distinct schedules.
• Examine tolerance development to d-amphetamine's behavioral effects.
• Determine factors influencing tolerance, specifically local vs. global response consequences.

Main Methods:

• Rats' key pressing behavior maintained under spaced-responding and random-ratio schedules.
• Administration of d-amphetamine (1.0 and 1.7 mg/kg) under a multiple schedule.
• Daily drug administration to assess tolerance development.
• Manipulation of schedule components (removal and reinstatement).

Main Results:

• D-amphetamine increased low rates of spaced responding and decreased high rates of ratio responding.
• Drug-induced changes reduced overall food delivery.
• Tolerance developed to ratio responding effects but not initially to spaced responding effects.
• Tolerance to spaced responding effects emerged rapidly when the ratio schedule was removed, and reversed upon reinstatement.

Conclusions:

• D-amphetamine exhibits schedule-dependent effects on operant behavior in rats.
• Tolerance development to d-amphetamine is influenced by global session-wide response consequences rather than solely local schedule components.
• The concept of 'response cost' in behavioral economics should consider total costs within a session.