The effects produced by prostaglandin D2 on serotonin turnover and release and tryptophan uptake

In earlier studies, it was proposed that there was a serotonergic involvement in the ability of prostaglandin D2 (PGD2) to potentiate pentobarbital sleeping time. The actions of PGD2 on neuronal turnover and release of serotonin and uptake of tryptophan were examined in mice. The effect of PGD2 administration on serum tryptophan levels was also investigated. PGD2 (1 and 4 mg/kg) increased the concentrations in whole brain of endogenous tryptophan (TRYP) and of 3H-tryptophan (3H-TRYP) following an intravenous (IV) injection of 3H-tryptophan. Formation of 3H-5-hydroxyindoleacetic acid (3H-5HIAA) was doubled after PGD2 administration (1 and 4 mg/kg). Whole brain concentrations of endogenous serotonin (5HT) and 3H-serotonin (3H-5HT) were unchanged after the administration of the prostaglandin. PGD2 (10(-4) to 10(-10)M) in vitro had no effect on spontaneous or K+-evoked release of 3H-5HT from whole brain synaptosomes. Uptake of 3H-tryptophan in synaptosomes was neither stimulated nor depressed by (10(-4) to 10(-12)M) PGD2. There was also no change in serum tryptophan levels after administration of this prostaglandin. Thus, PGD2 administration does affect the serotonergic system but no direct neurochemical correlate of sedation can be shown.