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