One of the difficulties in creating an animal model of autism is to demonstrate the characteristic symptoms of autism in the animal, i.e: impairment of socialization, abnormalities of communication, and limited activity and curiosity. We have recently established an autism model rat by exposing embryonic day (E) 9 rat embryo to either thalidomide or valproic acid (VPA). Significant increase of hippocampal serotonin (5-hydroxytryptamine), frontal cortex dopamine, and hyperserotonemia was observed in the E9 teratogen-exposed rats (Narita et al., Ped Res 2002). They also exhibited morphological change of the raphe nuclei (the 32nd Annual meeting of SFN, Orlando, 2002), increased expression of serotonin transporter gene (see the abstract of Nishigami-N et al.). In the present study, we have examined (1)Morris water maze test, (2)eight-arm radial maze test, and (3)open field test, that are commonly used for the rat behavioral studies. No significant changes were found in the water maze test. In the radial maze ...