Focal Injection of Ethidium Bromide as a Simple Model to Study Cognitive Deficit and Its Improvement.
BACKGROUND
Memory and cognitive impairments are some of devastating outcomes of Multiple Sclerosis (MS) plaques in hippocampus, the gray matter part of the brain. The present study aimed to evaluate the intrahippocampal injection of Ethidium Bromide (EB) as a simple and focal model to assess cognition and gray matter demyelination.


METHODS
Thirty Wistar rats were divided into three groups: control group, which received saline, as solvent of EB, into the hippocampus; and two experimental groups, which received 3 μL of EB into the hippocampus, and then, were evaluated 7 and 28 days after EB injection (n=10 in each group), using a 5-day protocol of Morris Water Maze (MWM) task as well as Transmission Electron Microscopy (TEM) assay.


RESULTS
Seven days after EB injection, the behavioral study revealed a significance increase in travelled distance for platform finding in the experimental group compared to the control group. In addition, the nucleus of oligodendrocyte showed the typical clumped chromatin, probably attributed to apoptosis, and the myelin sheaths of some axons were unwrapped and disintegrated. Twenty-eight days after EB injection, the traveled distance and the time spent in target quadrant significantly decreased and increased, respectively in experimental groups compared to the control group. Also, TEM micrographs revealed a thin layer of remyelination around the axons in 28 days lesion group.


CONCLUSIONS
While intracerebral or intraventricular injection of EB is disseminated in different parts of the brain and can affect the other motor and sensory systems, this model is confined locally and facilitates behavioral study. Also, this project could show improvement of memory function subsequent to the physiological repair of the gray matter of the hippocampus.
Department of Physiology and Pharmacology, School of Medicine, Alborz University of Medical Sciences, Karaj, Iran.
Mahdi
M
Goudarzvand
Department of Physiology and Pharmacology, Pasteur Institute, Tehran, Iran.
Samira
S
Choopani
Department of Anatomy, School of Medicine, Alborz University of Medical Sciences, Karaj, Iran.
Alireza
A
Shams
Department of Physiology, Faculty of Medicine, Tarbiat Modares University, Tehran, Iran.
Mohammad
M
Javan
Department of Nutrition, School of Medicine, Alborz University of Medical Sciences, Karaj, Iran.
Zohreh
Z
Khodaii
Department of Internal Medicine, School of Medicine, Alborz University of Medical Sciences, Karaj, Iran.
Farhad
F
Ghamsari
Department of Physiology and Pharmacology, Pasteur Institute, Tehran, Iran.
Naser
N
Naghdi
Department of Anatomy, Faculty of Medicine, Shahid Beheshti University of Medical Sciences, Tehran, Iran.
Abbas
A
Piryaei
Department of Physiology, Faculty of Medicine, Shahid Beheshti University of Medical Sciences, Tehran, Iran.
Abbas
A
Haghparast
Behavior; Ethidium bromide; Hippocampus; Rat; Remyelination