Metabolization of a retention-improving dosage of methylglucamine orotate in rat brain

The present study was carried out to investigate the time course of metabolization in brain and the influence on RNA synthesis of a retention-improving dosage of methylglucamine orotate after intracerebroventricular application. As determined by the HPLC technique, 73% of acid-soluble radioactivity were recovered in unmetabolized orotic acid 30 min after injection of 1 mumole methylglucamine [6-14C]orotate. Two hours later the amount of radioactivity found in this compound was negligible. Analysis of the sequence of labelling of uridine compounds revealed uridine to be the metabolite exhibiting the highest radioactivity at 30 min, whereas UMP- and UDP-sugars attained their maximum 90 min after injection of the precursor. Incorporation of [3H] guanosine into brain RNA was not altered by intraventricular application of 1 mumole methylglucamine orotate as compared to methylglucamine chloride-treated controls. The results are interpreted in the light of behavioural findings in which the pyrimidine nucleotide precursor at the dosage used improved the retention performance of an acquired behaviour in the rat.