A quantitative analysis of stereotyped gnawing induced by apomorphine.

An apparatus was designed and constructed to enable a quantitative analysis of the stereotyped gnawing produced by the dopamine agonist apomorphine. Using this apparatus it was discovered that increasing the subcutaneous dose of apomorphine increased (1) the number of animals that gnawed, and (2) the duration of gnawing in those animals that gnawed at all doses. Other aspects of apomorphine-induced gnawing, in particular the latency to respond and the frequency and duration of individual gnaws, were relatively unaffected. Likely properties of the system responsible for the organization of sterotyped gnawing are discussed.