Effect of protocatechuic acid on cognitive processes and central nervous system neuromodulators in the hippocampus, prefrontal cortex, and striatum of healthy rats.

Objective: : This study aimed to investigate the influence of protocatechuic acid (PCA) on learning, memory, and central nervous system (CNS) neuromodulators in healthy rats, to analyse whether the procognitive effects of PCA found in animal models of memory impairment and described in the literature occur in healthy individuals.

Methods: : PCA was administered for 48 days at doses of 50 or 100 mg/kg body weight. The cognitive performance was analysed in behavioural tests (open field, novel object recognition, water maze). Then the animals were sacrificed and their hippocampi, prefrontal cortices and striata removed to measure the level of serotonin, dopamine (DA), noradrenaline, their metabolites and amino acids (taurine, histidine, serine, glutamic acid, aspartic acid, γ-aminobutyric acid, alanine) using high-performance liquid chromatography.

Results: : No obvious behavioural changes were observed. Post-mortem quantification of monoamines showed that the turnover of DA in the striatum was significantly increased by PCA. Moreover, hippocampal, and cortical levels of histidine were influenced by PCA and significantly decreased.

Conclusion: : Despite many beneficial effects of PCA in experimentally developed cognitive impairments, it has no sharp effect on memory performance in healthy rats. The influence on the turnover of striatal DA and modulation of the amino acid system by affecting the concentration of histidine deserves a deeper examination due to the role of histamine in neuropsychiatric disorders as well as the functional interactions between histidine and DA metabolism in the brain.