Synaptic Reorganization in the Hippocampus in a Perinatal Rat Model of Hypoxia-Ischemia
Abstract number :
3.014
Submission category :
Year :
2001
Submission ID :
2108
Source :
www.aesnet.org
Presentation date :
12/1/2001 12:00:00 AM
Published date :
Dec 1, 2001, 06:00 AM
Authors :
P.A. Williams, DVM, Anatomy and Neurobiology, Colorado State University, Ft. Collins, CO; P. Dou, MD, Anatomy and Neurobiology, Colorado State University, Ft. Collins, CO; E. Dudek, PhD, Anatomy and Neurobiology, Colorado State University, Ft. Collins, CO
RATIONALE: One of the potential chronic consequences of perinatal hypoxia-ischemia is the development of epilepsy. Synaptic reorganization in the hippocampus has been associated with epilepsy after an injury. We tested the hypothesis that perinatal hypoxia-ischemia will induce synaptic reorganization in the dentate gyrus, and that these new circuits will lead to electrophysiological abnormalities.
METHODS: The right common carotid artery of 7-day-old rats was permanently ligated. The rats were placed for 120 min into a chamber filled with 8% oxygen (37[degree] C). Animals were directly observed for chronic seizure activity for 6-18 mo post-lesion. Extracellular recordings were obtained from the granule cell layer of the ipsilateral septal hippocampus with antidromic stimulation. The contralateral hippocampus and the recorded slices were processed for Timm staining.
RESULTS: One rat out of six was seen to have spontaneous motor seizures after the injury. The dentate gyrus from ipsilateral slices displayed all-or-none bursts of population spikes, when bathed in 30 [mu]M bicuculline and 6 mM [K+][sub]o[/sub] (n=3 out of 5). Sham-control hippocampi showed no abnormalities. The septal region from the ipsilateral hippocampus had increased amounts of Timm staining in the inner molecular layer (IML) as compared to the contralateral and sham-control hippocampi. However, the contralateral hippocampus from the epileptic animal did demonstrate an increase in Timm staining in the IML.
CONCLUSIONS: These results suggest that perinatal hypoxia-ischemia can induce synaptic reorganization in the lesioned hippocampus, and these new circuits can predispose the hippocampus to abnormal electrophysiological activity.
Support: NS10643 and NS16683