The effects of scopolamine on three different types of suppressed behavior of rats.

Twelve albino rats were trained to lever press on a variable-interval one min schedule for sweetened condensed milk reinforcement. While responding on this schedule a two minute tone was presented. For one group it signalled a response contingent shock (Punishment), for another group it signalled the delivery of an unavoidable non-contingent shock at its termination (CER) and for a third group, reinforcement was withheld during the tone (Extinction). In the first experiment scopolamine in doses of 0.8 to 12.8 mg/kg did not alter response rates during the tone for any group. In a second experiment 16 hooded rats were tested with 6.4 mg/kg of scopolamine using a similar procedure, but with different shock levels, apparatus, reinforcement and session duration. For all three groups the drug depressed responding during the tone. It was concluded that when all other aspects of the situation are equated scopolamine will produce the same effect on behavior suppressed by punishment, CER and extinction.