Prostaglandin D synthase in the prenatal ovine brain and effects of its inhibition with selenium chloride on fetal sleep/wake activity in Utero

Abstract

It has been proposed that prostaglandin (PG) D2 induces physiological sleep in mammals by acting on sleep centers located in the anterior hypothalamus. In fetal sheep, definitive rapid-eye-movement and non-rapid-eye-movement sleep states appear at ∼125 d gestation (term is ∼147 d). In adult animals, PGD synthase (PGDS) (functionally and structurally homologous to β-trace protein) is secreted into CSF with a circadian pattern, with the highest concentrations present during sleep. In this study we show that PGDS/β-trace protein is present in fetal sheep CSF at 125 and 135 d gestation but not at 90 d gestation. SeCl4, a specific inhibitor of PGDS, was given to unanesthetized fetal sheep (130-140 d gestation) by intracere-broventricular infusion at a dose of 25, 100, 500, or 1000 pmol/min for 4 hr. Artificial CSF was infused in control experiments. Arousal behavior, defined as the presence of nuchal muscle electromyogram activity, electro-ocular activity, and breathing movements during low-amplitude electrocortical activity, increased from 3.8 ± 1 min/hr to 6.6 = 0.5 and 7.0 ± 0.3 min/hr at doses of 100 and 500 pmol/min, respectively (p < 0.05). SeCl4 at 25 and 1000 pmol/min had no significant effect on arousal activity. Infusion of PGD2 at 500 pmol/min intracere-broventricularly for 4 hr decreased the incidence of arousal from 3.8 ± 0.5 min/hr to 0.7 ± 0.3 min/hr (p < 0.05). When 500 pmol/min PGD2 was infused immediately after a 4 hr infusion of SeCl4 (500 pmol/min), the SeCl4-induced increase in arousal behavior was abolished. Together, the presence of PGDS/βtrace protein in fetal CSF in late gestation and the effects of SeCl4 in increasing the incidence of arousal-like behavior suggest that PGD2 has a role in the induction and maintenance of prenatal sleep.