Quantitation of total MHPG in the rat brain using a non enzymatic hydrolysis procedure. Effects of drugs

Abstract

An acid-catalyzed procedure has been used to hydrolyze MHPG-sulfate in homogenates of rat brain. The samples (in 0.4 mol/L perchloric acid) are treated for 3 min. at 100°C in a water bath and aliquots are injected into a reversed phase HPLC system. Detection is achieved fluorimetrically. The absolute detection limit for MHPG is 150 pg, which allows the reliable determination of either free or total MHPG in rat brain in concentrations down to 15 ng/g, using the described procedure. The concentration of total MHPG found in the brains of saline-treated rats are which is in a good accordance with the concentration value for the same samples obtained using a GC-MS method (115 ± 19 ng/g). Rats treated with clonidine (300 μg/Kg, i.p.) or yohimbine (10 mg/Kg, i.p.) showed brain concentrations of total MHPG of 68 ± 22 ng/g and 299 ± 85 ng/g, respectively. The utility of this method for the analysis of brain regions or brain nuclei (e.g. locus coeruleus) is also shown.