Kindled Limbic Seizures and the Thalamus: Specific to the Midline Region
Abstract number :
2.079
Submission category :
Year :
2001
Submission ID :
800
Source :
www.aesnet.org
Presentation date :
12/1/2001 12:00:00 AM
Published date :
Dec 1, 2001, 06:00 AM
Authors :
J.M. Williamson, BS, Neurology, University of Virginia, Charlottesville, VA; E.H. Bertram, MD, PhD, Neurology, University of Virginia, Charlottesville, VA
RATIONALE: Growing data suggest that the midline thalamic nuclei are involved in several aspects of limbic seizures. In this study we wished to determine whether this involvement was specific to the midline nuclei, or whether there was a more generalized involvement of lateral thalamic nuclei as well.
METHODS: Adult male rats were used throughout this study. Bipolar electrodes were placed in
either the midline thalamic (MT) region (predominantly the medial dorsal nucleus) or the lateral thalamus (LT) at the same depth. Additional bipolar electrodes were placed in either the ventral hippocampus (HC) or the basal amygdala (AM). Rats were kindled with a rapid kindling protocol (6 stimulations daily, every other day; 10 sec, 1 ms biphasic 50 Hz) with stimulations to either thalamic region or to the AM or HC. Data were analyzed for the acquisition of behavioral seizures (BSS), electrographic seizures (ADD), afterdischarge threshold (ADT) and involvement of the secondary recording site.
RESULTS: Afterdischarge thresholds for the two thalamic regions were significantly higher compared to the AM or HC. It was particularly difficult to elicit afterdischarges from LT. LT kindling proceeded far more slowly than MT. Recruitment of AM and HC occurs much later in LT kindling than in MT, which recruited the two sites immediately. Recruitment of MT during HC and AM kindling is immediate whereas recruitment of LT from these structures occurred only in conjunction with convulsive behaviors.
CONCLUSIONS: These findings suggest that limbic kindling in the thalamus is restricted to MT. The data further indicate that MT and LT have a higher threshold for seizure induction compared to AM and HC. Overall the results suggest that MT is an early participant in limbic kindling and seizures, whereas LT is involved only as the seizures begin to generalize.
Support: NS-25605.