Biphasic effects of 3-quinuclidinyl benzilate on spontaneous motor activity in mice

Dose-response relationships for onset, duration, and magnitude of 3-quinuclidinyl benzilate (QNB) on spontaneous motor activity (SMA) were studied in mice. QNB was administered SC immediately before 2-h test sessions in dose levels differing by a factor of 0.5 log (range 0.1–10.0 mg/kg). For the total activity session of 2 h, QNB had a biphasic effect on SMA; at a low dose (0.1 mg/kg) it decreased, and at moderate to higher doses (0.3–10.0 mg/kg) it increased SMA in a dose-related fashion. The onset and duration of the significant decreasing or increasing effects were also dose-dependent; at the low dose (0.1 mg/kg) it depressed SMA from 5 to 35 min postinjection, at moderate doses (0.3 and 1.0 mg/kg) it enhanced SMA from 5 to 45 min and 5 to 70 min, respectively, postinjection. At the higher doses (3.0 and 10.0 mg/kg) it increased SMA within 5 min and lasted for 100 and 120 min, respectively. The increase in SMA for the dose range from moderate to high doses of QNB (0.3–10.0 mg/kg) was linear with dose. In general, QNB appears to produce a biphasic effect on SMA responding in mice.