Figure 1: Density of , , and receptor subunit-immunoreactive neurones in the PAG in (a) spontaneously cycling female rats and (b) rats that had undergone a progesterone withdrawal regime. Abbreviations: P: proestrus; O: oestrus; ED: early dioestrus; LD: late dioestrus; HP: high progesterone; VEH: vehicle treated; PWD: progesterone-withdrawn. for each group, all values . , post hoc Fischer test after significant ( ) one-way ANOVA. Data redrawn from [31, 32].