Effect of dietary amino acids on behavior and serum levels of amino acids in stress loaded rats

Interrelationships between behavior and concentrations of serum amino acids in stressed rats with immobilization and water immersion were investigated. Rats were subjected to 7 h of immobilization with water-immersion stress (IWS) in each sequential day, and serum amino acids were then determined. On the first day, serum taurine, threonine, valine, leucine, isoleucine, phenylalanine, lysine, and histidine (increased-type of amino acids) were significantly increased, but alanine (decreased-type) was significantly decreased. On days 3 and 7, the increase was retained, except for threonine, histidine, and lysine. Spontaneous activities (locomotion, rearing behavior, hole-poking) under loading water-immersion stress were significantly decreased, but a supplementation of branched-chain amino acids (BCAA) led to recovery. We suggest that pretreatment with some kind of increased type of amino acid, such as BCAA, might effectively prevent decline in spontaneous activities evoked by water-immersion stress.