MODIFIED SPONTANEOUS ACTIVITY RHYTHMS IN RATS

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Abstract
Thirty-two rats of an inbred strain were subjected to an artificial day length of 6 hrs. of light at 27[degree]C., and 6 hrs. of dark at 16[degree]C. for approx. 2 mos. Although no animal maintained a consistent 12 hr. rhythm for more than 37 days, 30 of 32 rats did exhibit 12 hr. rhythms for varying lengths of time. Spaying animals at the end of the 1st mo. of readings had no marked influence on the type of daily rhythm, although total daily activity was less. Rats can be induced to have 12 hr. spontaneous activity rhythms, i.e. 2 peaks of activity /24 hr. day, for varying lengths of time by controlling both temp. and light conditions.