Running wheel activity in hamsters with hypothalamic damage

The amount of wheel running activity by hamsters sustaining damage to the suprachiasmatic nuclei, adjacent hypothalamic areas or lateral geniculate nuclei was examined with numerical and actogram methods. The various hypothalamic lesions reduced activity in a region-specific fashion. Damage to the suprachiasmatic nuclei was associated with the most profound decrease in activity. Reduced daily wheel running was not necessarily correlated with lower activity levels as estimated from the actogram. Some animals with greatly reduced activity had actogram records with apparent increases in activity. The inconsistency between the actogram and numerical analysis was the product of an interaction between changes in running rate and length of activity bouts after lesions. These data indicate a role for the suprachiasmatic region in the regulation of level of activity. The analyses also show that the standard actogram can be a very poor index of changes in activity.