Central administration of L-ser-L-his and L-ile-L-his induced sedative effects under an acute stressful condition in chicks

Carnosine (beta-alanyl-L-histidine) is rich in the skeletal muscle and brain, but the function of dipeptides like carnosine in the brain has not been clarified. We previously showed that alanyl dipeptides with carboxyl terminal branched chain amino acids induced hyperactivity in chicks when intracerebroventricularly (i.c.v.) administrated. In the present study we investigated the effect of amino terminal histidine related dipeptides under isolation induced stress. I. c. v. injection of L-seryl-L-histidine and L-isoleucyl-L-histidine induced sedation with a weak hypnotic effect, and L-valyl-L-histidine lowered spontaneous activity in chicks. However, L-alanyl-L-histidine, glycyl-L-histidine and L-methionyl-L-histidine had no significant effects in all parameteres determined. These results indicate that L-seryl-L-histidine and L-isoleucyl-L-histidine dipeptides may be effective in improving anxiety and have novel functional effects in the brain.