Effects of scopolamine on locomotor activity and metabolic rate in mice

Reduction of metabolic rate occurs in rodents in response to intoxication with several chemicals, including amphetamine. In the present study, cholinergic mediation of locomotor activity and metabolic rate was investigated by measuring the effects of scopolamine on the frequency of photobeam breaks, the rate of CO2 production, and rectal temperature in unrestrained mice. Increasing doses of scopolamine (0, 0.3, 1.0, 3.0, and 10.0 mg/kg IP) increased locomotor activity over a 72-min observation period. CO2 production (as minute volume exhaled CO2, VECO2), measured simultaneously with locomotor activity, was suppressed equally at all doses of the drug. Rectal temperatures taken 72 min after scopolamine declined slightly in a dose-related manner. These results parallel earlier findings with d-amphetamine and suggest that divergent effects on metabolic rate and locomotor activity may be induced by centrally-acting compounds acting on more than one neurochemical system.