A COMPARISON OF CHLORPROMAZINE AND IMIPRAMINE ON BEHAVIOR OF THE PIGEON

¹ Department of Pharmacology, Harvard Medical School, Boston, Massachusetts

The effects of chlorpromazine and imipramine upon pigeons were contrasted in a complex behavioral situation. The experimental situation involved two keys, red (FI) and blue (FR): the first response on the former was reinforced after the conclusion of a 300-second interval and on the latter each thirtieth response was reinforced. The schedule was programmed so that responding on the blue key was reinforced several consecutive times while responding on the red key had no consequences and then the situation was reversed several times each session. The result was to create two complex concurrent behaviors on the two keys. In low doses imipramine increased the rate of responding on both keys without interfering with the control that the schedule and the discriminative stimuli existing in the experiment exerted upon the pigeons' behavior. However, during the period that the red (FI) key was reinforced, chlorpromazine selectively suppressed responding characteristic of fixed interval behavior on the red (FI) key. During the same phase in the schedule chlorpromazine increased unreinforced responding on the blue (FR) key; overall rate remained unaffected. High doses of imipramine increased overall rate still further but otherwise exerted effects similar to chlorpromazine.

Low doses of methamphetamine, like imipramine, increased overall behavior. Under the same schedule pentobarbital had effects very similar to those of chlorpromazine and produced changes that may be interpreted as representing diminished stimulus control. The chief effect of scopolamine was to reduce overall responding.

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