DIFFERENCES IN FEAR MOTIVATED BEHAVIORS AMONG INBRED MOUSE STRAINS

The behavioral performance of inbred mouse strains was examined in ani mal models of anxiety to evaluate the potential contribution of geneti c factors to fear-motivated behaviors. The preference that randomly br ed mice and rats exhibit for the enclosed as opposed to the open arms of an elevated maze has been considered a fear-motivated behavior. Pro nounced differences were observed in this measure among 16 inbred mous e strains. An estimate of the proportion of the variance attributable to between-strain differences, eta2, revealed that 78% and 69% of the variance in time and number of entries in the open arms of an elevated maze, respectively, can be attributed to genetic factors. In contrast , only 27% and 42% of the variance could be attributed to between-stra in differences in ambulatory activity in the open field and elevated m aze, respectively. Furthermore, performance in the elevated maze was p redictive of behavior in other animal models of anxiety. Thus, signifi cant negative correlations were observed among inbred mouse strains be tween the percent time spent in the open arms of the elevated maze and amplitude of an acoustic startle response (r(s) = - 0.88m P < 0.01) o r latency to initiate chow consumption in a hyponeophagia paradigm (r( s) = - 0.71, P < 0.05). These results indicate that genetic factors su bstantially contribute to fear motivated behaviors in these animal mod els of anxiety. The use of such inbred mouse strains may provide a nov el approach to investigate the biochemical and genetic bases of fear.