Dissociation of Persistent Estrus and a Free-Running Activity Cycle in Different Light Cycles

Abstract
Persistent estrus and free-running activity cycles of female albino rats have been shown in previous studies to develop in long photoperiods and non-24 h light cycles. In the present study, estrous cyclicity and running activity were monitored simultaneously in varying photoperiods (LD 12:12, 20:4, 22:2 and 23:1) and cycle lengths (22, 23, 24, 25 and 26.5 h). Contrary to expectations, there was no correlation between the induction of persistent estrus and a free-running activity cycle. The data support the notion that although estrous cyclicity and running activity are related, the controlling elements for these rhythms are separable.

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