Date of Award
Master of Arts
Dr. Alan D. Poling
Masters Thesis-Open Access
The acute and chronic effects of morphine were examined in pigeons exposed to a multiple schedule with fixed ratio 5, 25, and 125 components. Acute exposure to morphine (0.56-10.0 mg/kg) resulted in rate reductions under each component when the dose was 1 mg/kg or higher. With chronic exposure to 5.6 mg/kg, tolerance to the rate-reducing effects of morphine was evident under each fixed ratio component. The development of tolerance was determined to some extent by fixed-ratio size, a result similar to earlier findings with cocaine.
Nickel, Mark J., "Fixed-Ratio Size as a Determinant of the Development of Tolerance to Morphine" (1992). Masters Theses. 853.