Response suppression during cumulative dosing: a role for Pavlovian conditioning

Area of Science:

• Behavioral pharmacology
• Animal behavior studies

Background:

• Pigeon key pecking behavior is a standard model for studying drug effects.
• Understanding drug administration methods is crucial for accurate dose-response assessments.

Purpose of the Study:

• To investigate the impact of cumulative dosing procedures on cocaine dose-response curves in pigeons.
• To compare the reliability of cumulative versus noncumulative dosing methods.

Main Methods:

• Pigeons were trained on fixed-ratio or fixed-interval schedules for food.
• Cocaine cumulative dose-response curves were generated with saline and increasing cocaine doses.
• Dose-response curves were also assessed using noncumulative (pre-session and single-injection) methods.

Main Results:

• Repeated cumulative dosing shifted cocaine dose-response curves leftward, likely due to learned associations between dose size and administration time.
• Substituting saline for later doses initially maintained leftward shifts, but eventually caused rightward shifts.
• Noncumulative dosing procedures produced more repeatable results than cumulative dosing.

Conclusions:

• The observed shifts in dose-response curves under cumulative dosing may be influenced by conditioning factors.
• Noncumulative dosing procedures offer greater reliability for assessing drug effects in this model.