[Temporal characteristics of the behavioral effects of tuftsin].

Administration of endogenous immunostimulator, tuftsin, (0.3 mg/kg, i/p) in rats produced biphase behavioral response. The first phase lasted for about 30 min and was characterized by the enhancement of orientation behavior and suppression of startle reaction. During the second phase the orientation behavior was depressed and passive avoidance reaction intensified. The second phase lasted for at least 24 hours.