Apomorphine-induced locomotion and gnawing: evidence that the experimental design greatly influences gnawing while locomotion remains unchanged.

In a recent study we have shown that it was possible to recognize and record two independent behavioural patterns elicited by apomorphine (s.c.): one behaviour characterized by increased locomotion, sniffing and repetitive head and limb movements and another, characterized by compulsive gnawing. In the present study we have further characterized the gnawing and the locomotion patterns, their dependence on the experimental design and on the test environment. We found that the apomorphine-induced gnawing was easily modified by factors such as the design of the test-box and the habituation of the animal to the test-box. Locomotion, on the other hand was essentially independent of such factors and seemed more compulsive than the so-called "compulsive gnawing".