The effects of low-doses of microcystin-leucinearginine （ MC-LR ） exposure on neurobehaviors and N-acetylaspartate （NAA） expression in the hippocampus of rats were investigated. After male Sprague-Dawley （SD） rats were treated intra-gastrically with different doses of MC-LR for 90 d, the locomotor activity, spatial learning and memory function were evaluated in the rats after treatment using open field tests and Morris water maze tests. The results show that MC-LR exposure can lead to impairment of the spatial learning capacity and locomotor activity in rats at the dose of 2. 00 p,g/kg. The levels of NAA in the hippocampus were measured by magnetic resonance spectroscopy （MRI）. A significant decrease of NAA/Cr ratio （ P 〈 0. 05） was observed in the hippocampous. This study indicates that intra-gastrical exposure to low-doses of MC-LR has adverse effects on neuronal behavior and NAA levels in the hippocampous.
This paper deals with positive solutions of a degenerate parabolic system: u t= Δ u m+ v p ln α(h+u), v t= Δ v n+u q ln β(h+v) with homogeneous Dirichlet boundary conditions and positive initial conditions. This system describes the processes of diffusion of heat and burning in two component continuous media with nonlinear conductivity and volume energy release. We obtain the global existence and blow up results of the solution relying on comparison with carefully constructed upper solutions and lower solutions.
