Regional and age-related expression of gelatinases in the brains of young and old rats after treatment with kainic acid

Due to the possible detrimental impact of local inflammatory responses in n eurodegenerative disease, it was of interest to measure the expression of e xtracellular matrix-degrading enzymes, a group of proteases that are induce d during an inflammatory response, in the brains of old and young animals i n a model of neuronal death. Doses of kainic acid were administered that re sulted in comparable hippocampal pyramidal neuron loss in young and old F34 4/BN hybrid rats, even though each age group received widely differing dose s. Two matrix metalloproteinases (MMPs), MMP-2 and MMP-9, were differential ly induced with respect to time after kainic acid in sensitive brain region s in both young and old rats. However, the elevation of MMP-9 in the tempor al lobe 12 h after injection in old rats was significantly greater than tha t observed in young animals. These results suggest th at early and late ind uction of MM Ps may play a role in neuronal death and repair mechanisms, re spectively, and that inflammatory mechanisms in the central nervous system (CNS) of old rats are exaggerated compared to young rats. (C) 2000 Publishe d by Elsevier Science Ireland Ltd.