Manganese-enhanced magnetic resonance imaging in the acute phase of the pilocarpine-induced model of epilepsy.

Abstract

Magnetic resonance images are useful in the study of experimental models of temporal lobe epilepsy. The manganese-enhanced MRI (MEMRI) technique is of interest since it combines the effects caused by manganese on the increased contrast in activated cell populations, when competing with calcium in synaptic transmission. Thus, the purpose of this study was to investigate the temporal evolution of the contrast related to manganese in the acute phase of temporal lobe epilepsy induced by systemic pilocarpine and compare it to the expression of the c-Fos protein. During this phase, the intensity of the MEMRI signal was analyzed at three different time points (5, 15 or 30 minutes) after the onset of status epilepticus (SE). The group that was maintained in status epilepticus for 30 minutes showed a decrease in intensity of the signal in CA1 and the dentate gyrus (DG). There were no differences between the control group and the other groups treated with pilocarpine. The expression of the protein, c-Fos, in the same animals showed that even in the short-duration status epilepticus (5 minutes), there was already maximal cellular activation in subregions of the hippocampus (DG, CA1 and CA3). Under the experimental conditions tested, our data suggest that the MEMRI signal was not sensitive for the identification of detectable variations of cell activation in the acute phase of the pilocarpine model. Our findings are not consistent with the idea that manganese contrast reflects primarily alterations in cellular activity during SE when other signal-modifying elements can act.