Date of Graduation

1998

Document Type

Thesis

Degree Type

MA

College

Eberly College of Arts and Sciences

Department

Psychology

Committee Chair

David Schaal

Committee Co-Chair

Anne Watson

Committee Member

Anne Watson

Committee Member

David Schaal

Abstract

Three rats deprived to 80% of free-feeding weight pressed a bar to avoid electric shock in a Sidman avoidance procedure (20 s R-S interval, 5 s S-S interval). Once responding became stable, two of the rats were reduced to 70% of free feeding weight and one rat’s weight was increased to 95%. Cocaine (10.0, 17.0, 30.0, 40.0 mg/kg), morphine (5.6, 10.0, 17.0, 30.0, 40.0) and saline were tested in a random series with multiple determinations. Rate of responding and avoidance proficiency were recorded. When the injection series was completed the rats were free-fed and their weights redetermined so that the two rats that were at 70% of free-feeding weight were increased to 95% and the rat at 95% was reduced to 70%. Then the rats were tested again. Morphine produced little systematic change in rate or proficiency. Cocaine produced a dose-dependent increase in responding, but little change in proficiency. Economic versus stress hypotheses are discussed.

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