Soft-diet feeding decreases dopamine release and impairs aversion learning in Alzheimer model rats

• Published in: Neuroscience letters 2008-07, Vol.439 (2), p.208-211
• Main Authors: Kushida, S., Kimoto, K., Hori, N., Toyoda, M., Karasawa, N., Yamamoto, T., Kojo, A., Onozuka, M.
• Format: Article
• Language: English
• Subjects: Alzheimer; Alzheimer Disease - chemically induced; Alzheimer Disease - complications; Amyloid beta-Peptides; Animals; Avoidance Learning - physiology; Biological and medical sciences; Degenerative and inherited degenerative diseases of the nervous system. Leukodystrophies. Prion diseases; Diet - methods; Disease Models, Animal; Dopamine - metabolism; Dopaminergic system; Electrochemistry - methods; Fundamental and applied biological sciences. Psychology; Hippocampus - metabolism; Learning and memory; Learning Disorders - etiology; Learning Disorders - pathology; Male; Medical sciences; Microdialysis - methods; Neurology; Peptide Fragments; Rats; Reaction Time - drug effects; Reaction Time - physiology; Soft-diet feeding; Tyrosine 3-Monooxygenase - metabolism; Ventral Tegmental Area - metabolism; Vertebrates: nervous system and sense organs; β-Amyloid
• ISSN: 0304-3940; 1872-7972
• DOI: 10.1016/j.neulet.2008.05.017

To examine the effects of soft-diet feeding on the dopaminergic system in a model rat for Alzheimer's disease (AD), we measured dopamine release in the hippocampus using a microdialysis approach and assessed learning ability and memory using step-through passive avoidance tests. Furthermore, we immunohistochemically examined the ventral tegmental area (VTA), which is the origin of hippocampal dopaminergic fibers using tyrosine hydroxylase (TH), a marker enzyme for the dopaminergic nervous system. Feeding a soft diet decreased dopamine release in the hippocampus and impaired learning ability and memory in AD model rats in comparison with rats fed a hard diet; however, TH-immunopositive profiles in the VTA seemed not to be notably different between rats fed a soft diet and those fed a hard diet. These observations suggest that soft-diet feeding enhances the impairment of learning ability and memory through the decline of dopamine release in the hippocampus in AD rats.