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. Author manuscript; available in PMC: 2015 May 28.
Published in final edited form as: Physiol Behav. 2014 Apr 13;131:7–16. doi: 10.1016/j.physbeh.2014.04.006

Fig. 1.

Fig. 1

Plasma LH levels in hamsters transferred to a new cage with a novel wheel at ZT 5 on proestrus. Profiles of plasma LH concentrations (mean ± SE) are illustrated on expected proestrus (Day 1) and estrus (Day 2) from ZT 5–11. The shaded area indicates exposure to DD. Closed circles and solid lines depict LH levels in animals whose LH surge was blocked on proestrus and occurred on estrus. Open circles and broken lines depict LH concentrations in hamsters whose LH surge was not blocked. The ZT time at which peak LH levels occurred is indicated. Novel wheel-induced blockade of the proestrous LH surge occurred in 8/8 hamsters receiving an unlocked wheel and in 6/9 hamsters presented with a wheel that was locked from ZT 5–9 and is thus not dependent on exercise.