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