Food maintained responding by pigeons was suppressed by response-dependent electric shock presentation (punishment). Administration of 5.6 mg/kg pentobarbital IM for 25 days and, later, 10.0 mg/kg pentobarbital for 30 days resulted in profound, sustained, dose-related increases in punished responding and shock presentation.
Key words Pentobarbital - Punished behavior - Tolerance - Key peck - Pigeons