FSCV detects changes in GnRH release between two different biological states. A, Representative examples of the pattern of spontaneous GnRH release detected at CFMEs near GnRH soma/fiber appositions in the POA and fibers in the ME in ovariectomized mice treated with estradiol to induce diurnal changes in GnRH neuron activity (Christian et al., 2005). Data were collected in 1 min bins and each bar shows the maximum concentration in each bin. Multiple spikes in adjacent bin represent one long event. B–D, Mean ± SEM concentration change (B), event duration (C), and number of secretory events/h (D). Numbers in bars are number of cells (D) or number of events examined (B, C). AM, Morning; PM, afternoon; conc., concentration. *p < 0.05.