Long-term administration of Greek Royal Jelly decreases GABA concentration in the striatum and hypothalamus of naturally aged Wistar male rats

Royal Jelly (RJ) is a unique substance obtained from bees that has been used widely in European and Asian traditional medicine for its potential to prevent signs of aging through its antioxidative, anti-inflammatory, anti-hyperglycemic and anti-hypercholesterolemic properties. We recently reported an enhancement in spatial memory along with changes in monoaminergic transmission in aged rats after chronic RJ administration. Here, we aim to further explore the action of RJ on central nervous system activity by examining levels of amino acids in selected brain structures of aged male Wistar rats following 2-months of Greek RJ administration. RJ powder was previously chemically characterized and given orally (50 or 100 mg of powder/kg b.w./day) by gastric gavage. The concentrations of amino acids (alanine, aspartic acid, gamma-aminobutyric acid, glutamic acid, histidine and taurine) in the brain regions examined (prefrontal cortex, hippocampus, striatum and hypothalamus) were quantified using HPLC. We also examined basic biochemical parameters of renal and hepatic activity, as damage of these organs could potentially explain the changes in brain function and behavior. Upon biochemical examination, a decrease in the concentration of gamma-aminobutyric acid was observed in both the striatum and hypothalamus. Liver and kidney functions were not changed by chronic RJ-administration. Our results provide insight toward understanding the mechanism of action of RJ and its effects on neurotransmission in the central nervous system.