Sporadic dementia of Alzheimer's type induced by streptozotocin promotes anxiogenic behavior in mice.

Alzheimer disease, a form of dementia in which loss of memory is the first and the most characteristic symptom, is frequently accompanied by affective symptoms. Intracerebroventricular (i.c.v.) injection of streptozotocin (STZ) to rodents has been reported as an appropriate model for sporadic dementia of Alzheimer's type (SDAT), characterized by a progressive impairment of memory. However, very little or nothing is known about non-cognitive behavioral effects (e.g. anxiety-like behavior) in the STZ model. In this context, the hypothesis to be tested in this study is if i.c.v. injection of STZ (0.1mg/site, 4 μl) induces anxiety-like behavior in mice. The findings of the present study indicate that i.c.v. injection of STZ in mice resulted in an anxiogenic behavior. Mice spent less time and decreased the number of entries in the open arms in the elevated plus-maze task. The latency to the first entry in the dark side in the light-dark box task was reduced by STZ. No difference was found in anxiety-like behavior between early and late time (i.e., at 7 and 21 days after infusion, respectively). These results indicate that i.c.v. STZ injection caused an anxiogenic behavior in mice.