Stereotypic and hypothermic effects of apomorphine and N-n-propylnorapomorphine in mice

Abstract

Two dopaminergic agonists, apomorphine (APO) and N-n-propylnorapomorphine (NPA) were compared in mice for their ability to induce stereotypic cage-climbing and hypothermia. Stereotypic cage-climbing responses were recorded on videotape and subsequently rated “blind” in comparison to the animal's predrug behavior and to the behavior of animals administered control solutions. Hypothermia was measured as changes from predug body temperature. Both APO and NPA produced statistically significant cage-climbing and hypothermia vs. controls. Dose—response analyses (0.5–10 mg/kg, i.p.) indicated that on a milligram basis the two drugs induced similar magnitudes of stereotypic activity. In contrast, dose—response analyses (0.008–40 mg/kg, i.p.) of APO and NPA induced hypothermia suggested an approximate 90-fold greater effect for NPA. These results suggest that there may be two different types of dopaminergic systems responsible for the hypothermic and stereotypic responses measured.