Amygdalar kindling is associated with elevated zinc concentration in the cortex and hippocampus of rats

The reported convulsant properties of zinc and its association with hippocampal function prompted investigation of zinc levels during the induction and maintenance of kindling. Rats were fed zinc adequate diets during kindling, incited by daily amygdalar stimulation. The concentration of zinc in hippocampus was unperturbed during 3 stages of kindling induction when compared to either naive, sham surgery, or electroshock controls. In contrast, cortical zinc increased during kindling induction but returned to control levels in fully kindled animals. Two weeks after full kindling was established, the concentration of zinc in the hippocampus and overlying cortex increased significantly, in the absence of further electrical stimulation. The effect was restricted to the central nervous system inasmuch as zinc levels were unaffected in liver and other extracerebral tissues. Moreover, the zinc concentration was relatively unchanged during the 24 h period following a single electroconvulsive seizure, implying that the observed changes were not simply a postictal phenomenon. The results of this study suggest that long-lasting elevations in zinc are present after kindling is established. Whether this finding is related to the perpetuation of abnormal neuronal excitability or represents a compensatory response remains to be elucidated.