Effects of lateral and medial septal lesions on various activity and reactivity measures in rats.

Roles of the lateral and medial septum in the regulation of activity, reactivity and open field behavior in rats were examined in the present study. Effects of lateral, medial and combined lateral and medial septal lesions were studied, respectively. Our results indicate that lateral septal lesions significantly decreased locomotor activity and tended to decrease rearing response. While it also markedly increased movement time in the activity monitor, stereotyped behavior and tactile startle amplitude. The most significant findings with medial septal lesions were decreased activity, especially in the center area of an open field and decreased exploratory behavior in rats. For most behavioral measures, effects of combined lateral and medial septal lesions were similar to that of medial septal lesions alone except that it augmented startle response with a different response pattern compared to that of lateral septal lesions alone. The locomotion patterns of these animals also revealed some qualitative difference in their behavior. These results are further discussed in the scope of anatomical, neurochemical and pharmacological differentiations of the septum complex.