Involvement of serotonergic neuronal systems in the estrogen-induced afternoon prolactin surge : time-dependent changes in serotonergic neuronal activities in discrete brain nucllei

In this study, the involvement of the serotonergic neuronal systems in the estrogen-induced afternoon prolacin (PRL) surge was investigated. The induction of the afternoon PRL surge was confirmed using blood samples collected by both catheter and decapitation in the ovariectomized (OVX) estradiol (E_2)-treated rats. The contents of serotonin (5-HT) and 5-hydoroxyindole acetic acid (5-HIAA) in the following brain nuclei at 0900, 1500, and 1800 h were measured simultaneously using HRLC-ECD method [medial preoptic nucleus (POM), anterior hypotharamic nucleus (AH), suprachiasmatic nucleus (SCN), ventromedial (VM), and dorsomedial (DM) hypothalamic nuclei, arcuate nucleus (ARC), periventricular hypothalamic nucleus (PE), amygdala (AM), dorsal (RD) and medial (RM) raphe nuclei]. In OVX vehicle-injected rats, significantly lower were the contents both of 5-HT in any nuclei and of 5-HIAA in any nuclei excluding the PE and AM at 1800 h