Propagation of amygdala-kindled seizures to the hippocampus in the rat: electroencephalographic features and behavioural correlates.
BACKGROUND
The propagation of amygdala-kindled seizures to the dorsal and ventral hippocampus was examined, in rats. The relation of contralateral seizure propagation to the onset of generalized convulsions was also studied.


METHODS
In all subjects, electrodes were implanted in the amygdala. Two additional electrodes were implanted (bilaterally) in the dorsal (n = 6) or ventral (n = 8) hippocampus. Kindling stimulations were delivered twice daily (interval 4 h).


RESULTS
Initially, triggered after-discharges (ADs) were recorded only in the amygdala. With repeated stimulation, the AD propagated to the hippocampus. Rates of propagation were as follows (mean # of stimulations +/- SEM): ipsilateral ventral hippocampus, 4.0 +/- 0.9; ipsilateral dorsal hippocampus, 6.2 +/- 1.4; contralateral dorsal hippocampus, 7.5 +/- 1.4; contralateral ventral hippocampus, 8.5 +/- 1.0. AD propagation to contralateral sites was significantly slower than to ipsilateral sites. Ipsilateral hippocampal recruitment occurred between stages 1 and 2 (partial seizures), whereas contralateral hippocampal recruitment occurred between stages 2 and 3 (transition to generalized seizures).


CONCLUSIONS
These results indicate that during amygdala-kindling, it takes several stimulations before discharge propagates to the hippocampus. The close link between contralateral hippocampus involvement and seizure generalization warrants further study, and may lead to a better understanding of the pathways involved in seizure spread.
Hewapathirane
D Sesath
DS
University of Toronto Epilepsy Research Program and Department of Pharmacology, University of Toronto, Toronto, Ont., Canada M5S 1A8. sesath.hewapathirane@utoronto.ca
Burnham
W McIntyre
WM
D000679:Amygdala / Q000503:physiopathology*; D000818:Animals; D001522:Behavior, Animal / Q000502:physiology*; D004569:Electroencephalography; D006624:Hippocampus / Q000503:physiopathology*; D007696:Kindling, Neurologic / Q000502:physiology*; D008297:Male; D051381:Rats; D017207:Rats, Sprague-Dawley; D011999:Recruitment, Neurophysiological / Q000502:physiology; D012640:Seizures / Q000503:physiopathology*