Administration of protocatechuic acid affects memory and restores hippocampal and cortical serotonin turnover in rat model of oral D-galactose-induced memory impairment.

Protocatechuic acid (PCA) is a phenolic compound believed to have neuroprotective and procognitive activity. d-Galactose (D-Gal) is a sugar, which administered to mammals can induce cognitive deficits. The first aim of this study was to confirm the effectiveness of D-Gal administered orally in inducing cognitive impairment in rats and describe how it affects the concentration of neurotransmitters in rats' brain. The second aim was to evaluate the influence of PCA on learning, memory and neurotransmission in D-Gal-exposed rats. Memory impairment was induced by long-term administration of D-Gal (100 mg/kg body weight/day) directly via oral gavage. PCA (50 or 100 mg/kg body weight/day, respectively) was administered in drinking water. Morris Water Maze test (MWM) to assess learning and spatial memory was initiated after 38 days of treatment and lasted for 10 days. The concentrations of monoamines and their metabolites were evaluated in selected brain regions using high performance liquid chromatography. D-Gal significantly impaired cognitive performance during the acquisition and recall of MWM compared to control rats and changed concentrations of cortical serotonin as well as its cortical and hippocampal turnover. The turnover of dopamine was also influenced by D-Gal. Simultaneously, PCA was found to improve retrieval of acquired information in MWM and to restore brain serotonergic and dopaminergic turnover dysregulated by D-Gal. These findings confirm the usefulness of oral D-Gal in eliciting rat model of mild memory impairment and show that long-term administration of PCA can be beneficial in reversing detrimental changes related to cognitive deficiencies.