The hippocampus in spontaneously hypertensive rats: a quantitative microanatomical study

The influence of hypertension on the morphology of hippocampus was assessed in spontaneously hypertensive rats of two, four and six months and in age-matched normotensive Wistar-Kyoto rats. Values of systolic pressure were slightly increased in two-month-old spontaneously hypertensive rats in comparison with age-matched Wistar-Kyoto rats and augmented progressively with age in spontaneously hypertensive rats. No microanatomical changes were observed in the hippocampus of spontaneously hypertensive rats of two months in comparison with age-matched Wistar-Kyoto rats, whereas a decrease of white matter volume was observed in the CA₁ subfield and in the dentate gyrus of four-month-old spontaneously hypertensive rats. In the hippocampus of six-month-old spontaneously hypertensive rats a reduction of grey matter volume both in the CA₁ subfield and in the dentate gyrus, a loss of neurons affecting to a greater extent the CA₁ subfield and an increase of glial fibrillary acid protein-immunoreactive astrocytes was found. The occurrence of apoptosis and/or necrosis identified using the terminal deoxyribonucleotidyl transferase-mediated biotin-16-dUTP nick end labelling technique was also observed in the CA₁ subfield and to a lesser extent in the dentate gyrus. The only change noticeable in the CA₃ subfield of six-month-old spontaneously hypertensive rats was a slight increase in the number of glial fibrillary acid protein-immunoreactive astrocytes.These findings indicate the occurrence of neuronal loss and of astrocyte changes in the hippocampus of spontaneously hypertensive rats of six months, being the CA₁ subfield the area most affected. The relevance of these neurodegenerative changes in hypertension and the possible occurrence of apoptosis and/or necrosis as expression of hypertensive brain damage is discussed. Copyright (C) 2000 IBRO.