Reversal of scopolamine induced amnesia in rats by the steroid sulfatase inhibitor estrone-3-O-sulfamate

Enhancement of hippocampal acetylcholine release by the neurosteroid dehydroepiandrosterone sulfate: an in vivo microdialysis study

The effect of dehydroepiandrosterone sulfate (DHEAS) administered i.p. on the release of acetylcholine (ACh) from the hippocampus of anesthetized rats was examined using in vivo microdialysis. DHEAS significantly increased ACh release above the pre-treatment levels for all doses tested. The administration of 100 mg/kg significantly enhanced ACh release greater than 4-fold when compared to the saline-treated group 80 min following drug administration. This study is the first to demonstrate that the neurosteroid DHEAS, a negative allosteric modulator of the GABAA receptor, can enhance the release of ACh from neurons in the hippocampus.

Pharmacokinetics of oestrone-3-O-sulphamate

The sulphatase pathway is thought to be the major route of oestrogen synthesis in breast tumours in postmenopausal women. There is currently considerable interest in developing a potent steroid sulphatase inhibitor to block oestrogen synthesis by this route. One of the most potent inhibitors discovered so far is oestrone-3-O-sulphamate (EMATE) which is active in vivo. In this study we report the preparation of a formulation for the administration of EMATE by the oral route. A method, using high-performance liquid chromatography (HPLC), was also established to measure concentrations of EMATE in rat plasma after its oral or i.v. administration. Using the oral formulation and HPLC assay, EMATE was readily detected in rat plasma after oral administration. Plasma EMATE concentrations were related to the dose of drug administered orally over the 10-40 mg/kg range. To examine the pharmacokinetics of EMATE, the compound (40 mg/kg, single dose) was administered either orally (in the formulation) or i.v. (in propylene glycol) with plasma samples being collected for up to 6 h. After oral administration, EMATE was rapidly absorbed, with the peak plasma concentration being detected at 30 min, after which plasma concentrations rapidly decreased. After i.v. administration a plasma EMATE concentration was detected at 1 h similar to that after oral administration. The clearance of EMATE from plasma followed a bi-phasic curve, showing an initial half-life of 30 min, followed by a slower half-life of 4 h 30 min. Little evidence was obtained for any metabolism of EMATE to oestrone. Rat liver sulphatase activity was almost completely inhibited (>99%) within 30 min of oral or i.v. administration of EMATE.