Timed changes of synaptic zinc, synaptophysin and MAP2 in medial extended amygdala of epileptic animals are suggestive of reactive neuroplasticity

Repeated seizures induce permanent alterations of the brain in experimental models and patients with intractable temporal lobe epilepsy (TLE), which is a common form of epilepsy in humans. Together with cell loss and gliosis in many brain regions, synaptic reorganization is observed principally in the hippocampus. However, in the amygdala this synaptic reorganization has been not studied. The changes in Zn density, synaptophysin and MAP2 as markers of reactive synaptogenesis in medial extended amygdala induced by kainic acid (KA) as a model of TLE was studied. Adult male rats (n = 6) were perfused at 10 days, 1, 2, 3 and 4 months after KA i.p. injection (9 mg/kg). Controls were injected with saline. The brains were processed by the Timm's method to reveal synaptic Zn and analyzed by densitometry. Immunohistochemistry was used to reveal synaptophysin and MAP2 expression. A two-way ANOVA was used for statistics, with a P < 0.05 as a significance limit. Normal dark staining was seen in all medial extended amygdala subdivisions of control animals. At 10 days post KA injection a dramatic loss of staining was observed. A slow but steady recovery of Zn density can be followed in the 4 month period studied. Parallel, from 10 days to 2 months stronger synaptophysin expression could be observed, whereas MAP2 expression increased from 1 month with peak levels at 3–4 months. The results suggest that a process of sprouting exists in surviving neurons of medial extended amygdala after status epilepticus and that these neurons might be an evidence of a reactive synaptogenesis process.