An improved method for detecting drug effects in the open field.

A double test cross-over design was applied to the testing of rats in the open field. When used to examine the effects of atropine, chlorpromazine and lysergic acid diethylamide (LSD) on open field behaviour, this design proved 4--40 times more sensitive than the previously popular single test design. In no case was the double test design less sensitive. Results are discussed in relation to screening of medically useful compounds.