Kindling phenomena induced by the repeated short-term high potassium stimuli in the ventral hippocampus of rats: on-line monitoring of extracellular glutamate overflow
Y. Ueda et al., Kindling phenomena induced by the repeated short-term high potassium stimuli in the ventral hippocampus of rats: on-line monitoring of extracellular glutamate overflow, EXP BRAIN R, 135(2), 2000, pp. 199-203
We observed in this study that transient periodic stimuli in response to hi
gh potassium (40 mM, 5 min at 40-min intervals, 13-15 stimuli) perfusion in
the ventral hippocampus of rats led to the appearance of a kindling-like p
henomenon. In this kindling-like phenomenon, we confirmed the augmentation
of glutamate release and the prolongation of spike discharge. Changes in th
e extracellular glutamate levels before and after the stimuli were monitore
d by the application of in vivo microdialysis combined with on-line enzyme
fluorometric detection of glutamate. This kindling-like phenomenon was not
observed when microdialysis was carried out using a Ca++-free medium. The a
ugmentation of glutamate release and the prolongation of spike discharge wi
th epileptic convulsions are completely Ca++ dependent. These data show tha
t repeated short-term increases in extracellular glutamate levels results i
n the enhancement of excitatory neuronal systems, causing an excessive prop
agation of seizure activity and culminating in secondary generalized seizur
es.