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. Author manuscript; available in PMC: 2015 Jul 1.
Published in final edited form as: J Steroid Biochem Mol Biol. 2013 Apr 10;0:132–141. doi: 10.1016/j.jsbmb.2013.03.010

Fig. 4.

Fig. 4

Rodent age impairments in the E2-induced gonadotrophin surge. Redrawn from Anderson et al. 2002 [78]. Hypothalamic-pituitary impairments in the induced LH surge in acyclic rats (18 month, PVC). Top panel: experimental design, with E2 implants to ovariectomized rats (OVX). Bottom panel: Young cycling rats OVX and given E2 implants had a nocturnal LH surge which models the pre-ovulatory blood LH surge at proestrus, whereas middle-aged acyclic rats did not respond. Notably, LH was elevated in the young OVX rats without E2 (−), but not in the old, showing impaired negative feedback of low E2 on pituitary secretion of LH.