The Bulletín of Kanagawa Dental College

Vol. 37 No. 1       MARCH- 2009

ISSN: 0385-1443      UBIC: 65

ABSTRACT

In order to establish a framework to understand the effects of dysfunctional mastication caused by soft-diet feeding on the dopaminergic neural system in both normal and Alzheimer's disease (AD) brain, we assessed dopamine (DA) release in the hippocampus using a micro-dialysis approach and learning ability and memory using step-through passive avoidance tests. In addition, we assessed the levels of tyrosine hydroxylase (TH), the ratelimiting enzyme, for the biosynthesis of dopamine in the ventral tegmental area (VTA), using immunohistochemical methods. The results showed that when amyloid-E ¿protein infused rats were fed a soft diet, a decrease in DA release occurred in the hippocampus, and learning ability and memory were observed to diminish in comparison with rats that had been fed hard food. However, no change in the number of TH-immunopositive neurons was observed in the VTA of rats with dysfunctional mastication requiring a continuous soft diet. These observations suggest that soft-diet feeding may enhance a decline in hippocampal dopaminergic neuronal systems and result in impaired learning ability and memory in AD brain. Key words: Dopaminergic system / Soft-diet feeding / β-amyloid / Tyrosine hydroxylase.

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