Anatomy Department, Tehran Medical Sciences University, Tehran,Iran
Introduction: The septal area is an important telencephalic center that plays a prominent role in the learning, emotional sexual behaviour processes and autonomic functions. This area contains two main divisions; lateral (LS) and medial (MS), that receive numerus afferents from hippocampal formation. This study compares, quantitatively distributional pattern of the afferent neurons to these two major subdivisions of septal area from hippocampal formation. Materials and Methods: In two different groups of male rats, stereotoxic injection of one microlitre HRP (25%) by using hamilton syringe into medial and lateral septal areas. After 48-72 hours, the brains were perfused and fixed through the left ventricle. The brains were removed and 70 micrometer coronal sections were cut from the basal forebrain part. TMB-histochemical reaction was performed on them. Then sections were counterstained by Neutral Red. Results: Following injection into each part, retrogradely labeled neurons were observed in the CA1-2 fields of Ammons horn, presubiculum and subiculum. Number of labeled neurons following injection into lateral septum were highly more than that of injection into the medial septum. In comparison to MS group, the neurons in LS group were also more intensely stained. Conclusion: Regarding to the results of this study it could be concluded that however, both lateral and medial septum receive afferents from hippocampal formation, there is a strong quantitative distributional discrepancy on the hippocampal origin of these afferents, that could be the basic for different functional roles of these areas.