CONSERVATION OF LOCOMOTOR BEHAVIOR IN THE GOLDEN-HAMSTER - EFFECTS OFLIGHT CYCLE AND A CIRCADIAN PERIOD MUTATION

Locomotor activity in rodents is restricted temporally by the animal's circadian system. The relative stability of both the species-specific pattern and the amount of locomotor activity per cycle suggested that this behavior may be regulated by conservative mechanisms. In these e xperiments, the wheel-running behavior of golden hamsters carrying the circadian period mutation, tau, was analyzed in animals housed in a 2 4-h light:dark cycle (LD) and in constant dark (DD) conditions to dete rmine which aspects of this behavior were conserved. In DD, apart from the change in period which defines the mutation, no main effects of a llele combination were found in either average amount of activity, act ivity profile, or length of the activity phase. In LD, wild-type behav ior did not differ from that in DD; however, heterozygous mutants exhi bited early onsets of activity, significant fragmentation of both acti vity and rest, an increase in the duration of the active phase, and an overall decrease in the amount of activity. Despite these differences , the total amount of time spent on the wheel in LD or DD was the same for all environment/genotype combinations. The data show that a conse rvative mechanism that may influence daily patterns of locomotor behav ior is related more to a drive to perform the behavior than the quanti ty or timing of the behavior itself. (C) 1998 Elsevier Science Inc.