Improvement of melatonin to the learning and memory impairment induced by amyloid beta-peptide 25 - 35 in elder rats.
OBJECTIVE
To investigate improvement of melatonin on learning and memory impairment induced by amyloid beta-peptide 25 - 35 (Abeta25-35) in elder rats.


METHODS
Step-down type passive avoidance test, shuttle-box test, and Morris water maze were used together to determine effects of Abeta25-35 and melatonin on learning and memory. Pathological changes were observed by HE, Congo red, and Ag staining.


RESULTS
The elder rats were injected bilaterally Abeta25-35 20 microg into the hippocampus to induce learning and memory dysfunction. Melatonin administration (0.1, 1, and 10 mg/kg, ig x 8 d) to the Abeta25-35-treated rats prolonged the latency, shortened the total stimulating time, and decreased the number of errors in the step-down test. Shuttle-box test showed that melatonin improved amnesic rats' performance at the same doses. Melatonin (0.1, 1, and 10 mg/kg ), giving for 10 d, could enhance the spatial resolution of amnesic rats in Morris water maze test. Also in Abeta25-35-treated group, a decrease in the number of neurons in cortex and hippocampus, a massive glial reaction, and neurophilic phenomenon were detected by HE staining; the positive vascular amyloidosis by Congo red and fibrils by Ag staining were observed. Melatonin (0.1 and 1 mg/kg)could inhibit above pathological changes in Abeta25-35 group.


CONCLUSIONS
Melatonin improved the impaired learning and memory induced by Abeta25-35 in elder rats.
Shen
Y X
YX
Institute of Clinical Pharmacology, Anhui Medical University, Hefei 230032, China. shenyuxi@mail.hf.ah.cn
Wei
W
W
Yang
J
J
Liu
C
C
Dong
C
C
Xu
S Y
SY
D016229:Amyloid beta-Peptides; D000818:Animals; D000975:Antioxidants / Q000494:pharmacology; D001362:Avoidance Learning / Q000187:drug effects; D018782:Maze Learning / Q000187:drug effects; D008550:Melatonin / Q000494:pharmacology*; D008568:Memory / Q000187:drug effects*; D008569:Memory Disorders / Q000139:chemically induced / Q000503:physiopathology*; D010446:Peptide Fragments; D051381:Rats; D017207:Rats, Sprague-Dawley
D016229:Amyloid beta-Peptides; D000975:Antioxidants; D010446:Peptide Fragments; C074636:amyloid beta-protein (25-35); D008550:Melatonin