title: Reduced hippocampal manganese-enhanced MRI (MEMRI) signal during pilocarpine-induced status epilepticus: edema or apoptosis?
abstract: Manganese-enhanced MRI (MEMRI) has been considered a surrogate marker of Ca(+2) influx into activated cells and tracer of neuronal active circuits. However, the induction of status epilepticus (SE) by kainic acid does not result in hippocampal MEMRI hypersignal, in spite of its high cell activity. Similarly, short durations of status (5 or 15min) induced by pilocarpine did not alter the hippocampal MEMRI, while 30 min of SE even reduced MEMRI signal Thus, this study was designed to investigate possible explanations for the absence or decrease of MEMRI signal after short periods of SE. We analyzed hippocampal caspase-3 activation (to evaluate apoptosis), T2 relaxometry (tissue water content) and aquaporin 4 expression (water-channel protein) of rats subjected to short periods of pilocarpine-induced SE. For the time periods studied here, apoptotic cell death did not contribute to the decrease of the hippocampal MEMRI signal. However, T2 relaxation was higher in the group of animals subjected to 30min of SE than in the other SE or control groups. This result is consistent with higher AQP-4 expression during the same time period. Based on apoptosis and tissue water content analysis, the low hippocampal MEMRI signal 30min after SE can potentially be attributed to local edema rather than to cell death.
authors.affiliation: Departamento de Fisiologia, Universidade Federal de São Paulo-UNIFESP, São Paulo 04023-06, SP, Brazil; Centro de Imagens e Espectroscopia in vivo por Ressonância Magnética (CIERMag), Instituto de Física de São Carlos, Universidade de São Paulo (IFSC-USP), São Carlos 13566-590, SP, Brazil.
authors.forename: Jackeline Moraes
authors.initials: JM
authors.lastname: Malheiros
authors.affiliation: Departamento de Neurologia e Neurocirurgia, Universidade Federal de São Paulo-UNIFESP, São Paulo, SP, Brazil.
authors.forename: Daniele Suzete
authors.initials: DS
authors.lastname: Persike
authors.affiliation: Departamento de Nefrologia, Faculdade de Medicina da Universidade de São Paulo, São Paulo, SP, Brazil.
authors.forename: Leticia Urbano Cardoso de
authors.initials: LU
authors.lastname: Castro
authors.affiliation: Departamento de Nefrologia, Faculdade de Medicina da Universidade de São Paulo, São Paulo, SP, Brazil.
authors.forename: Talita Rojas Cunha
authors.initials: TR
authors.lastname: Sanches
authors.affiliation: Departamento de Nefrologia, Faculdade de Medicina da Universidade de São Paulo, São Paulo, SP, Brazil.
authors.forename: Lúcia da Conceição
authors.initials: Lda C
authors.lastname: Andrade
authors.affiliation: Centro de Imagens e Espectroscopia in vivo por Ressonância Magnética (CIERMag), Instituto de Física de São Carlos, Universidade de São Paulo (IFSC-USP), São Carlos 13566-590, SP, Brazil.
authors.forename: Alberto
authors.initials: A
authors.lastname: Tannús
authors.affiliation: Departamento de Fisiologia, Universidade Federal de São Paulo-UNIFESP, São Paulo 04023-06, SP, Brazil. Electronic address: lcovolan@unifesp.br.
authors.forename: Luciene
authors.initials: L
authors.lastname: Covolan
mesh_terms: D000818:Animals; D020346:Aquaporins / Q000378:metabolism; D053148:Caspase 3 / Q000378:metabolism*; D006624:Hippocampus / Q000378:metabolism / Q000473:pathology*; D008279:Magnetic Resonance Imaging / Q000379:methods; D008297:Male; D010862:Pilocarpine; D016760:Proto-Oncogene Proteins c-fos / Q000378:metabolism; D051381:Rats; D013226:Status Epilepticus / Q000139:chemically induced / Q000378:metabolism / Q000473:pathology*
chemical_list: D020346:Aquaporins; D016760:Proto-Oncogene Proteins c-fos; D010862:Pilocarpine; D053148:Caspase 3
keywords: Apoptosis; Edema; Epilepsy; Hippocampus; Manganese-enhanced magnetic resonance imaging; Pilocarpine