Drug effects on the performance of pigeons under a negative automaintenance schedule

Pigeons were exposed to a negative automaintenance schedule in which food was delivered following brief key illumination only if the illuminated key was not contacted; contact of the lighted key prevented food delivery. All subjects emitted some responses under this procedure when drugs were not given. However, the number of responses was less than that which occurred under an automaintenance procedure in which food followed key illumination regardless of the bird's behavior. Under the negative automaintenance procedure, acute administration of atropine (0.01--0.1 mg/kg), d-amphetamine (0.4--1.6 mg/kg), and morphine (3,8--15 mg/kg) reduced in a dose-dependent manner the percentage of key illuminations in which subjects contacted the lighted key. Diazepam (1.0--6.0 mg/kg) increased the percentage of key illuminations during contact responses occurred.