Kruashvili L, Beselia G, Chkhikvishvili N (2019) Effect of medial septal selective and non selective lesions on exploratory behavior and recognition memory. Neuroscience 2019 Abstracts 336.01. Society for Neuroscience, Chicago, IL.
Summary: Investigation of cholinergic system and memory interaction has especially become the object of scientific attention due to the clinical and experimental data, in which the severity of dementia in Alzheimer’s disease (AD) was found to have a positive correlation with the extent of the cholinergic loss. The septum is connected to the hippocampus via the fimbria-fomix, which carries projections from the medial septum (MS), and the vertical limb of the diagonal band of Broca. These projections are predominantly cholinergic and GABAergic. Lesions of the fimbria-fomix, or electrolytic lesions of the MS, impair hippocampal- dependent learning and memory. The purpose of this study was to investigate ability to acquire and use spatial (or non-spatial) information as well as to habituate exploratory activity over time in sham-operated, electrolytic, neuro or immunotoxic MS lesioned rats. Methods: A total of 39 male rats were used. For electrolytic lesions a stainless steel was inserted in the MS. All injections were performed stereotaxically. Rats were individually given five 3-min sessions in the open field. All experiments were approved by the Animal Care and Use Committee of the Center and were in accordance with the principles of laboratory animal care. Results: Examination of the AChE stained sections showed that after injections of 192 IgG saporin into the MS, animals exhibited significantly less AChE staining in MS and hippocampus as compared to sections obtained from control animals. The MS electrolytic and ibotenic acid lesioned rats showed an increase in their exploratory activity to the objects and were impaired in habituating to the objects in the repeated spatial environment, rats with immunolesions of the MS did not differ from control rats. Electrolytic lesions of the MS disrupt spatial recognition memory, rats with immuno- or neurotoxic lesions of the MS were normal in detecting spatial novelty. The MS lesioned and control rats clearly reacted to the object novelty by exploring the new object more than familiar ones. Conclusions: MS is sufficient for spatial recognition, but is not sufficient for object recognition memory, the selective loss of septohippocampal cholinergic or noncholinergic projections does not disrupt the function of the hippocampus to a suffi cient extent to impair spatial recognition memory. Therefore, the present study demonstrates dissociation between the two major components (cholinergic and noncholinergic) of the septohippocampal pathway in exploratory behavior assessed in the open field.
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