ADMINISTRATION OF Aβ 25 35 IS NOT NEUROTOXIC TO THE SEPTO HIPPOCAMPAL CHOLINERGIC SYSTEM IN RATS

The β amyloid protein(Aβ) is the primary constituent of senile plaques in Alzheimer's disease(AD). Recent evidences have demonstrated the neurotoxicity of Aβ in vitro and in vivo. The selective degeneration of neurons in the septo hippocampal cholinergic system is one of the neuropathological features of AD. Nevertheless, the reports concerning effects of Aβ on the septo hippocampal cholinergic system were relatively few, especially, it is fairly poor in the morphological field. In this article, it was evaluated whether Aβ exerts neurotoxic effects on the septo hippocampal cholinergic system by choline acetyltransferase(ChAT) immunohistochemical and acetylcholinesterase(AChE) histochemical methods. The results were as follows: Microinjection of Aβ 25 35 into the medial septal nucleus of rats didn't result in any change in the morphology and number of the ChAT positive neurons in the medial septal nucleus and AChE positive fibers in the hippocampus after a 14 day survival time as compared with control groups, nor did microinjection of Aβ 25 35 into the hippocampus. These results suggest, under the condition studied, we don't observe any effect of Aβ 25 35 on the septo hippocampal cholinergic system in rats. It remains to be further investigated whether Aβ is neurotoxic in different laboratory conditions and animal species and self protection mechanism. (Figures 1～6 on plate 49)