Proceedings of The Physiological Society
University College Dublin (2009) Proc Physiol Soc 15, PC64
Effect of β-amyloid injection in hippocampus or olfactory bulb in an animal model
R. Guevara-Guzman1, C. Bernal1
1. Fisiologia, Universidad Nacional Autonoma de Mexico, Mexico, Distrito Federal, Mexico.
Alzheimer disease (AD) is the most common cause of dementia in old age. It is a public health problem in several countries. β-amyloid is a neurotoxic peptide that forms neuritic plaques in the brain of AD patients. Nevertheless, this impairment in memory is not the first symptom, as it is preceded by an olfactory deficit which also appears in some other neurodegenerative diseases that are into dementia. Olfactory impairment caused by in situ β-amyloid injection has not been assessed in an animal model, neither the correlation of neuronal impairment in different sites of injection: olfactory bulb (OB), hippocampus (HIPP) and entorrinal cortex. Therefore, the aim of this research work is to assess if the β-amyloid peptide injected in the olfactory bulb (Group 1) or hippocampus (Group 2) of the rat (under chloral hydrate (400 mg/kg, i.p.) anaesthesia) produces alteration in the social, olfactory and spatial memory. To assess olfactory behavior, we carried out different olfactory tests, in addition to other behavioral and biochemical tests. We detected olfactory behavior impairment in the group injected in the hippocampus in regards to the control group. The olfactory tests showed: a) inability to find a chocolate chunk hidden during the search test; b) inability to discriminate between the two scents in a discriminating test. However, not significant difference in the investigation time during the two encounters of the social recognition test was found. A similar increase of lipoperoxidation was showed, not only in the HIPP, but also in the entorrinal cortex and OB in group 2; whereas group 1 showed higher levels of lipoperoxidation in OB than in the HIPP. We may infer that the β-amyloid injection in HIPP produces olfactory impairment in the rat throughout oxidative stress process in this structure, which extends to the OB and the entorrinal cortex. The doses injected in OB did not cause an extensive impairment in the olfactory behavior as the one in HIPP.
Where applicable, experiments conform with Society ethical requirements