Effects of apomorphine on punished and unpunished responding in the rat.

Apomorphine has been reported to increase shock-suppressed drinking, which suggests that it might have antianxiety activity. Because some drugs that increase shock-suppressed drinking are not active in other punishment procedures, the effects of apomorphine on punished and unpunished responding maintained by a multiple fixed-interval, fixed-interval schedule of food presentation were studied in rats. At doses from 3.125 to 100 micrograms/kg, apomorphine failed to increase punished or unpunished responding. In contrast, pentobarbital produced large increases in punished responding maintained by a fixed-interval schedule of food presentation.