Modeling the LH Surge in Mice

The LH surge paradigm was modeled after the injection paradigm used in Bosch et al. (41 (link)) Female mice were bilaterally ovariectomized and were allowed to recover for 5 days. After recovery, animals were subcutaneously injected at ZT10 with 0.25 µg of β-estradiol (EB; catalog no. E8875; Sigma-Aldrich. St Louis MO) dissolved in 100 µL of sesame oil (catalog no. S3547; Sigma-Aldrich). The following day, the female mice were subcutaneously injected with 1.5 µg of EB dissolved in 100 µL of sesame oil and soiled male bedding added to the cage. The following day (7 days after ovariectomy), the female mice were either euthanized or bled at ZT12 (lights off) and blood was collected for LH analysis. A mixed cohort of surge mice were sampled the following morning at ZT2 (AM) to establish negative feedback LH levels. We used a conservative surge threshold of the average AM LH level plus 2 SD (42 (link)).