MESSENGER RNA EXPRESSION CHANGES IN CHRONICALLY INJURED EPILEPTOGENIC AND NONEPILEPTOGENIC RAT NEOCORTEX
Abstract number :
2.084
Submission category :
Year :
2003
Submission ID :
4095
Source :
www.aesnet.org
Presentation date :
12/6/2003 12:00:00 AM
Published date :
Dec 1, 2003, 06:00 AM
Authors :
Kevin D. Graber, Paulo F. Fontoura, Lawrence Steinman, David A. Prince Neurology and Neurological Sciences, Stanford University, Stanford, CA; Neurology, Hospital Egas Moniz, Lisbon, Portugal
Penetrating brain injury frequently results in epilepsy, often presenting after a latent period. In the rat undercut model of posttraumatic epileptogenesis, epileptiform abnormalities can be found ~ two weeks later, however, tetrodotoxin (TTX) treatment acutely following injury prevents epileptogenesis. We have previously examined mRNA expression changes that occur acutely after trauma, during a critical period for epileptogenesis. To better understand epileptogenesis and examine like-injured epileptogenic and nonepileptogenic cortex, in this study we examined alterations in mRNA expression occurring chronically in this model.
Undercut lesions were placed in sensorimotor cortices of 4 week-old male Sprague-Dawley rats, and sustained-release resin containing TTX, or control resin was placed subdurally over the injured area. One week later the resin implants were removed under anesthesia. Control animals underwent anesthesia, but no surgery was performed. Twenty days later, lesioned and control neocortices were removed and rapidly frozen. RNA was isolated and probes constructed for hybridization to Rat Genome U34A gene microarrays (Affymetrix). Three arrays were used per condition, using probes originating from 2 different animals per array. Significant differences were ascertained using Microsuite Array 5.0 and count and percentage analysis options of Data Mining Tool 3.0 (Affymetrix).
Of 8,784 target sequences on the arrays, stringent comparison of epileptogenic to na[iuml]ve cortex revealed an increase in 256 sequences and a decrease in 29. Comparison of TTX-treated and untreated injured cortex, revealed an increase in 12 target sequences (6 identified genes), and a decrease of 11 sequences (5 genes).
In contrast to previous studies of acutely injured cortices, mRNA expression changes present chronically after injury are relatively fewer in number, as expected. Results show that alterations in gene expression are critically dependent on the time point examined following injury, and suggest that the molecular mechanisms for establishment versus maintenance of posttraumatic epileptogenesis are likely to be significantly different.
[Supported by: NIH Grants NS02167, NS12151, and the Phil N. Allen Trust]