Previous studies have shown that αCalcium/Calmodulin dependent protein kinase II(αCaMKII) plays important roles in not only learning and memory but also aggressive and fear response in mice. To further understand roles of αCaMKII in brain function, we have generated transgenic mice overexpressing αCaMKII in forebrain. Interestingly, these mutant mice showed increase in anxiety in open field and elevated zero maze tests and increase in offensive aggression in resident-intruder test. Increase in anxiety observed in these transgenic mice suggests that expression level of CaMKII positively correlates with expression of anxiety related behavior. We next examined effects of administration of selective serotonin reuptake inhibitor (SSRI) on anxiety related behavior observed in these mutant mice. Treatment of these transgenic mice with SSRI suppressed anxiety-related behavior in both tests. These results raise the possibility that these mutant mice is a mouse model of anxiety disorder, that allows to develop therapeutic drugs . In addition, we have examined the expression profile of these mutant mice with or without the treatment of SSRI and tried to find out the anxiety-related genes. [J Physiol Sci. 2006;56 Suppl:S63]