Abstract

The environmental stress may produce to behavioral changes. In this study using a rodent stress model that exposure to the repetitive restraint stress elicits behavioral alterations, especially changes the patterns of the innate behavior but not the contextual memory and learning abilities. Nine weeks old Sprague-Dawley male rats were given the restraint stress (the stressed group) for 6 hours per day for seven consecutive days. The stressed rats were indicated the retarded development within the stressed-session compared to the control group. After the exposure to restraint stress for seven days, the rats' brains were performed to the NADPH-diaphorase stain on the limbic region of the brain. In the stressed animals have increased the counts of the neuronal nitric oxide synthase (nNOS) active neurons in the central amygdala of the brain. For behavioral assessments, animals were subjected to the exposure to novel environment-open-field apparatus-in order to examining the exploratory behaviors especially the ambulatory activity after the stress paradigm. The stressed animals indicated a significantly higher ambulatory activity for 5 min compare to the control animals. Moreover, the zone analysis of the tracking of exploration in open-field monitoring system, the stressed rats were a significantly decreased their activities in the center of arena compared to the control rats. However, the stressed rats were repetitively exposed to the same arena at once per day for 3 consecutive days, which ambulatory activity did attenuate to the control levels 3 days after exploration. These results suggested that the increase of counts of the nNOS reactive neurons in the central amygdala area due to the experience of repetitive stress paradigm can alter the eliciting pattern of the innate behavior and which has not been modulate the contextual learning and memory functions of the brain. (Korean J Str Res 2011;19:107∼114)

• Keywords: Restraint stress, Open-field activity, Anxiety, Learning and memory, Amygdala