Tomohisa Mori, Kenshi Murase, Jiro Tanaka and Yasuyuki Ichimaru (*)
Drug Discovery, Pharmaceutical Research Center, Meiji Seika Kaisha, Ltd., 760 Morooka-cho, Kohoku-ku, Yokohama 222, Japan
(*) To whom correspondence should be addressed.
Abstract: Effects of D3-receptor agonists, 7-OH-DPAT and PD128907, on the D1-receptor agonist SKF81297-induced hyperactivity in mice were examined. 7-OH-DPAT and PD128907 significantly suppressed the SKF81297-induced hyperactivity at low doses, but significantly potentiated the hyperactivity at high doses. These D3-agonists alone had no effect on the motor activity. A kappa-receptor agonist that reduces dopamine release had no effect on the SKF81297-induced hyperactivity. These results suggest that lower doses of 7-OH-DPAT and PD128907 may negatively influence the D1-receptor mediated behaviors via post synaptic D3-receptors. On the other hand, higher doses of these compounds may positively influence these behaviors via D2- or D3-receptors.
Keywords: D1-receptor agonist, D3-receptor agonist, Motor activity