Effect of clonidine, amphetamine, and their combinations on the locomotor activity of CD-1 and C57BL/6 mice.

Clonidine inhibited the exploratory motor activity of C57BL/6 mice non-habituated to the testing conditions. In CD-1 mice clonidine did not depress exploratory activity but did elevate the basal locomotor activity of animals both non-habituated and habituated to testing conditions. Amphetamine increased the locomotor activity of many C57BL/6 mice and conversely inhibited the locomotion of many CD-1 mice. In both strains, amphetamine in doses up to 2 mg/kg was unable to alter effects produced by clonidine. Results suggest that the locomotor activity of C57BL/6 mice is more sensitive than that of CD-1 mice to drugs affecting the central noradrenergic system.